I assume you are using Win 10 (?).

Disable Fast Startup and see if that fixes it or at least lets you into the BIOS.

See this tutorial on how to turn off fast startup:

https://www.tenforums.com/tutorials/4189-turn-off-fast-startup-windows-10-a.html

Did you ever find a solution @SPCQC ?

I have the same issue.

Thanks for the suggestion @fireberd , but that's not related to the situation at all. The system simply won't POST after  REBOOT command from Windows. You can then hold down the power button and hard power down. Then hitting the power button again will let it POST just fine.

With this situation, Windows updates will fail as will all BIOS updates. I am stuck on BIOS A02. I am thinking that this version of the BIOS is the issue and would love to flash to the latest. I have tried using Dell Support Assist and manually downloading the executeable BIOS A20 update. Both fail because restart fails. Therefore, flashing never takes place. When powering up again, you can go into BIOS and see that it is still A02.

HELP!

NO post means what, use the intel rules on names ?

• no power
• no post (no post means it never starts the scan or never finishes the scan, or if working right tells you what is wrong.)
• no boot.

3 stages of serial power on  events, 

tell all you see, first the screen, the LEDs, (4 LED codes behind black plastic on some dells)

Power button color LED and if blinks and if blinks how does it blink (codes)

do not remove GPU cards or insert them until you pull the AC line and do the reset, first. 5 steps.

or you will blow up mobo or cards, or more. ok>

NEVER EVER FLASH A BAD PC ok?  gee the A2 ran for how many years now, and was ok.

Your problem is dead screen RIGHT. focus on dead screens always and means BIOS is dead

or the PC needs the long hard reset. (sleep mode fails do that with BAD DRIVERS)

when any PC goes dead the last  thing to think about is BIOS UPDATES, ok? (or you will brick the PC)

so with GPU card out and monitor connected to iGPU ports, now, it fails, now you know the GPU card is not the cause, and a great first test. in all PCs. but my guess is you dont know how to strip a PC down? is that it?

nor doing the hard long reset posted on every PC makers web site on earth?

(cures latchup, ESD and sleep failures and AC power surge events , that is why all PCs on earth have this page)  or near.

any time a PC acts dead or black screens or F2 and F12 hot keys are dead we do this. first, not flash BIOS ever.

here. 4 steps.

my 3020 run w10,64bit 100% solid, but I do not use sleep mode and if wise do not use that, unless you are 100% sure your  drivers to all chips present, (yah GPU too) are 100% good for sleep ,many are not.

in CP click power and turn off all sleep modes. if PC runs perfect you learned why it is failing. (OS upgrades love to land you here)

my w10 is fresh 1903 from MS. direct. is yours, it was installed with ethernet to lan working and not one dell chip on board fails, not ONE. Always shuts off and reboots prefect off my SSD, are you on SSD if not why not?

do not run rust drives to boot from, those days are gone. ($20 128GB drive is dirt chip run one?)

i could answer 10x better but I'd have to see all you did there and screen results and more.

this PC has F12 diagnosics  run ePSA yet

this PC has beep codes, get those ever,

or SMART errors, the POST has many errors on this PC vast in fact.

make sure the SMART = Enable is on in BIOS first.  keep it on.

page 39 in your service manual shows. power lamp codes, do you get those?

off
off
system is OFF
off
breathing
system is in sleep state
blinking
off
power supply unit (PSU) failure
steady
off
PSU is working but failed to fetch code
off
steady
system is ON
Amber LED State
Description
2,1
system board failure
2,2
system board, PSU or PSU cabling failure
2,3
system board, memory or CPU failure
2, 4
coin-cell battery failure
2,5
corrupt BIOS
2,6
CPU configuration failure or CPU failure
2,7
memory modules are detected, but a memory failure
3,1
possible peripheral card or system board failure
3,2
possible USB failure
3,3
no memory modules are detected
3,4
possible system board error
3,5
memory modules are detected, but a memory configuration or compatibility error
3,6
possible system board resource and/or hardware failure
3,7
some other failure with messages on screen
39

after replacing a COIN cell set the BIOS to defaults (f2 screen)

then turn off PXE. (thin net remote server boot not for you) disable this, now.

then BOOT ORDER PAGE F2., set HDD or Better SSD0 to BOOT first.

bingo if the drive is good it boots. from dead cold hard boots, not sleep,,  sleep takes vastly more software magic to work and not FAIL.

alternate way 1 and 2.

also if confused,  as many are on locked up PC.

just pull the AC plug from the wall and wait 24 hours, and see the PC is ok now. (until sleep fails)

way2:

the ICH chip will respond if you hold the power button for 5 seconds, this rule is in the silicon ICH, hard logic.

use that to learn whats up? 

w10 has no start button reboot, it has shutdown and restart and more but not reboot, sorry.

Post photos of rear of your PC and inside left, side lid off, then we can see what YOU HAVE.

F2 screens must work if not we focus like laser beam on that hard failure. (forget windows) F2 must work.

Unfortunately, it does the same thing on Win7 and disabling it changes nothing.

It does the same thing on Win7, even though I disabled Fast Boot.

The computer was still on warranty so I shipped it back.

never say you have the same issue, you will never know that. I promise you.

learn that PC has vast single point failures.  Ok VAST. never hyjack and assume things, it only makes your  PC problems hard to fix and muddies the poor OP's  issues.  this is no toaster, it's a computers. sorry.

focus on YOUR PC only and your evidence not stated. even start your own post.(always #1 best choice)

and all things connected outside and inside your PC not stated.

"REBOOT command from" (  I guess you meant to say RESTART?)

I say do not use the lame support assistant,  it causes huge problems, google it , see? ( It is a toy)

run epSA first and on hdd if present, do you boot from RUST drives. that be first to say. no>?

run smart tests on your unstated HDD0 or SSD0 we have no idea at all what is inside any Desktop (options vast)

nor of you removed all USB devices first to see if restarts (right word) fails.

are your running windows 10 64bit from MS direct>? v1903 or 09? type winver in run box, mine shows 1909.

is the device manager clean?  all chips show OK>??? no yellow , red marks , NO UNKNOWN FLAGs

are all MS updates up to date.?

if you use CP + power (control panel) and set up a custom power profile (advanced) and turn off speed junk

does the PC run ok now,(junk means bad drivers love to fail sleep, we all know that and we for sure assume that any time you have power issues be on that (sleep bull) like a tick on a hound dog tail.. YAH

but I can be all wrong, I cant see you , your  PC what it has connected or what screens do nor if BIOS screens go dead or error codes or beep codes are any of that, even the lack of errors, speaks to me.

nor if you turned off features in BIOS. like smart = enabled, (be so)

but do tell the full story , the OP removed the GPU card,  that would hide the nasty bad sleep mode drivers, to it and be care, a wise step. I go way farther testing:

stripping a PC to minimum. (on hard nut cases I sure do)

trying a test SSD (i keep spares on had $20each) and load w10 fresh here,  and be Ethernet connected to the router, at install time.

does the PC work now, yes, then you know old OS is bad, or old HDD was bad.

I then run full and complete smart tests on any RUST drive. (like step one on all PCs that act funny) why delay .

@savvy2 

Great response!
I will try to flesh out my posts better!
This is a barebones working unit that I am refurbishing. It currently has an i3-4160, 2x4GB DDR3 1600Mhz RAM, Samsung 860 EVO 250GB SSD for SATA-0 and the oem dvd drive for SATA-1. It has only the iGPU being used and no add-in cards. It only has usb keyboard and mouse plugged in along with ethernet.

When I power up the computer, the power button LED goes solid white and I don't see any diagnostic lights. It boots right into windows 10 1903 Pro. No complaints or warnings in Device Manager. 

So I go online and download the latest BIOS A20. I right click it and Run As Administrator. It opens up and compares BIOS versions, then I click OK and it attempts to Restart. However, no Restart occurs, after waiting for minutes or hours. This same behavior occurs when I click Restart after selecting the Power Button icon in the Windows Start menu.

I do not use Sleep. I have selected the High Performance power plan.

I have disabled S4 and S5 sleep in the BIOS.

I hope I have not missed anything. I can create my own post if the OP is done with this post.

Edit*

I just tried to use F12 to flash a BIOS from a bootable USB drive. The utility loaded the BIOS, then said it would need to Reboot. I clicked ok, and the screen went blank. I get no BIOS Spash Logo, same as when the I tell windows to Restart. After waiting a while, I hard powered off. Then powered on and it has the same BIOS and went straight to windows.

Can anyone understand the rambling of savvy2's reply?

The reboot problem has nothing to do with the OS. 
My Optiplex 3020 has the very same issue...no soft restart and stuck at BIOS ver A2.
The system has been stripped down to the bare bones in the diagnosis process.
My guess is at a later BIOS version it MAY fix the soft restart, but not sure.

Symptoms:
If you shutdown from the OS, it will shut down completely and power turns off.

If you try to restart from the OS, it will shut down the OS, but the power will remain ON.
You then need to press and hold the power button which will shut down the PSU.

To restart, you press the power button. Power will pop on and then quickly turn off again.
Pressing the power button a second time and the PC will boot normally.

The inability to soft restart also seems to prevent the system from updating the BIOS.

I have tried booting from a USB stick using GRUB4DOS and running the BIOS update from there. No Joy.
I also started a topic at Tom's Hardware addressing both the BIOS and Soft Restart issue.
See: https://forums.tomshardware.com/threads/dell-3020-cannot-update-bios.3562982/

The only thing not tried so far is setting the service jumper to closed and trying the bios update again.

Hey MSHarris,

You tired chaning the jumper yet? I have a fair few at where i work with the same issue and i am stumped.

here I will rumble  again (for me? I can not edit posts, no mater how I try, just one post works, sorry.

you can not uptate a2 to a20 (is general rule, on many)

the BIOS updates each a text file, I think marked on the DELL screen as more information? read those

it tells you the NO LONG JUMP rules,,  I have 3020MT and updates were super easy doing F12 update

but I read the info files,  and did as it told me, not to do any A2 long jump, as that will not work.

these words should be on the main dell 3020 update bios page at the top but is not. sad no?

the instructions stated turn UEFI off to legacy, did you> (and is vague that,  lots of UEFI choices there)

the instructions are painful, sure.

A10 states this.

For Windows 7 OS users, please install Microsoft KB931125 to prevent the invalid Digital Sign.       

Please make sure you suspend BitLocker encryption before updating BIOS on a BitLocker enabled system.

update  to. say A7 first the first urgent. then a10 , a15 then a20,  I just looked and could not find the NO LONG JUMP rule now, seen on many many a dell.

I wish I could see your screens, rule one for me, is never BIOS update any PC if the PC is not working right,

for example a bad PSU, (old PSU with bad caps and now huge noise on the power rails) bad to the bone there.

the PC must be stable, even booting it to LINUX demo USB  stick and testing the PC in LINUX demo mode.

learn how burning EEPROM works,  if the timings or power get off the flash fails and you bricked a PC.

but that is bumbling ,right.? good luck,  we can not see your PC screens nor test the PC.

WE can not know what  NO POST means unless stated, in words or screen shoots.

( it is good that this PC is at A2 means others didn't brick it flashing WRONG.