Help with Optiplex 9020 BIOS issue

This might be caused by Shutdown problems. The computer is not actually shutting down completely. Event Viewer might show an error about not shutting down correctly. I followed the directions in the link below and made a shutdown shortcut. I also used the other suggestions about turning off Fast Startup as well as changing settings in Power Plans to disable Hibernation and Hybrid Sleep. Not sure which one cured it, but after using the tips for awhile, I can now use the usual way to shutdown by right clicking on the Start Button and choosing Shutdown.

How To Properly Shut Down A Windows 10 PC (lifehacker.com.au)  

Thanks for the reply! unfortunately I just tried both of these methods and it's still the same( I don't think it's a shut down issue since I've been turning it off from the power strip everytime inbetween the shut down and the auto power up so it shuts down fully everytime, and then as soon as it receives electricity it will power up again...

First, try changing the size 2032 CMOS battery.  A bad battery will cause seemingly unrelated bizarre problems, including boot problems & etc.  With 1 refurb I bought, the first thing I had to do was change the battery.

Please see screengrab.  Never mind the "Hibernate" part, just make power button setting is on shut down.  (Personally, mine is on sleep so I don't accidentally shut off the PC.)

Sorry to hear you're in a region where power is unreliable.  I'd advise against BIOS update.  You already know how easy an MB can brick, and power and internet connections need to go uninterrupted.

If you do go for BIOS update, it was a previous generation BIOS updates needed to be done in an increment or two guided by the Dell site.  I don't know it to be that way for the 9020.

Reminder, it's normal for an Optiplex to power on for a second or two when power is introduced, then shut off again.

Are you using Win10 or power button to attempt to shut off PC?

Unless you have power spikes, normally, you shouldn't need to keep PC shut off at the power strip.

Hopefully you are not using power button to shut off.

You can shut down from the start menu under power

How to Shutdown Windows from Command Prompt

Open command prompt (Open run, type in ‘cmd’ and press enter)

Execute the command below  shutdown /s

This displays a message in blue background which says "You’re about to be signed out. Windows will shutdown in less than a minute.  press close.

The computer will shutdown in 60 seconds.

This is a force shutdown, so any open applications would close automatically without saving.

Thanks for the reply Brad! 

I have tried changing the cmos battery but it still behaves the same way. I've already changed the power button behavior to shut down suggested by @Mary G and then the force shut down command .

And about what you said :

 "Reminder, it's normal for an Optiplex to power on for a second or two when power is introduced, then shut off again."

Mine actually does that after a cold boot but then it starts booting up legit after that. And I've tried shutting off from windows and the power button but it still behaves the same after (it powers up)

And I've owned several PCs before in the same setup (even a 3020 with almost exactly the same specs I have now but I never had to completely cut power to them from the power strip and I almost always just shut them down or leave on sleep.

You're welcome!

I wondered before if it's the PSU.  Now I also wonder if it needs a Windows reload.