Re: All the software being used is standard off-the-shelf programs.

most likely boot issue is not due to hardware if fresh clean install gives smooth boot consistently.

do not install any app now, manually turn off Windows 10 update, run the pc for a few days and check for boot stability.  
if good, install only one app you need the most and test again for a few days.

@Pwalker21 - Define "Boot Failures" - Do you get an error message or does something else happen...?

What color is PC's power button, and steady or blinking, when it won't boot? If blinking, count the blinks because that's an error code.

What external devices are connected, aside from mouse, monitor, and keyboard?

Do you have an add-in video card (which one) or only onboard Intel UHD Graphics?

What type video port is used on monitor and on PC? And if you have an add-in video card, the first monitor should be connected to the card, not to onboard Intel UHD Graphics.

Thanks.

By boot failure I mean the computer appears to power on normally but the screen is completely blank.  There are no error messages or any indication of any activity.

On those occasions where I needed to reinstall Windows completely the Dell Support Assistant generally indicated there was a BIOS problem which it attempted to repair and reported that it had been prepared successfully.  However, that did allow Windows to boot.

To the best of my knowledge, the failure to boot did not follow the installation of Windows updates or at least not on the next restart.

Efforts to resolve the issue with a Windows Repair disk were unsuccessful after the first few times the problem arose.  

1) no error message just a blank screen.

2) Power button is white and steady no blinking.

3) Seagate External Drive, Brother printer, audio out cable.

4) Nvidia Graphics card

5) Display port and single monitor

Re: By boot failure I mean the computer appears to power on normally but the screen is completely blank. 
It seems when screen was completely blank, you were able to restart pc and get boot screen video using installation media.  Is that correct?  that would mean it could not boot from storage device for some reason, but had no trouble booting from installation media usb or dvd.

If the bios is corrupted, you would not be able to have any video on screen, i.e., no POST, no matter what boot device you use.

Thanks.

1) No blinking cursor just an illuminated normal screen.  I have not waited until the monitor goes into power-saving mode.

2) Nvidia GTX 1600 Ti which is connected to the monitor.  There is an Intel UHD Graphics 630 also which is not being used.

3) Always the monitor is powered on first.

4) I can certainly switch to HDMI for a test.  Thanks for the suggestion.

Since the power button is solid white, the PC has completed the POST successfully, but there's no video signal output.

Do you see anything on the monitor at all, eg a blinking cursor, or does monitor go into Power Saving Mode, or..?

Exactly which NVidia video card?

Since you have an NVidia video card, the monitor should be connected to that card, not to an onboard Intel UHD Graphics DP port. Note: CPUs with an "F" in their name (eg, i5-10400F) don't support onboard Intel UHD Graphics at all.

Are you powering the monitor on first, before you power the PC on?  Is this a 4K monitor?

Try switching to HDMI(video card)>HDMI(monitor).

Thanks.

I apologize if I have not explained the image on the monitor clearly.  Initially is indicated "No Signal" and then the screen is fully illuminated when the computer is powered on but there is no message or activity.   I suspect there is no successful POST on these occasions.

I have accessed the Boot Sequence through F2 and by switching the Boot Order to DVD I was able once or twice to resolve the problem by using a Windows Repair Disk.

That approach has not worked recently and so I resorted to accessing the tools available through F12.  There I would run whatever tests seemed available and the only time any issue ever presented itself was an indication there was a BIOS problem which the machine then proceeded to fix and reported as being fixed.  However, after that, the problem remained.

The next thing available as far as I could see was to do a complete restore of the OS using the tools available through F12 and that has always worked the way it should.  Of course, to make the machine usable all software than has to be reinstalled and files recovered.

I have not recently tried to boot from a DVD or USB installation media as it seemed easier and faster to just reinstall from the tools available at F12.  It is quite likely there would be no problem using either of these alternatives but they have not been tested.

So the monitor is not seeing a video signal, as I suspected, even though the PC completed the POST (solid white power button).

Can you test this monitor on a different PC using same DP cable and a DP port on the other PC, or a different monitor and different DP cable on this PC using DP on the NVidia card?

Is monitor correctly set to use DP? Some monitors have to be set manually on their own On-Screen Display (OSD) for the correct video input signal. If yours has an "auto detect" function in its OSD, disable it, if possible, and set monitor to use DP.

Did you mean a GTX 1660 Ti video card?  Is this a Dell OEM video card or is this an "after-market" card? If it's not a Dell OEM card, Secure Boot has to be disabled in BIOS setup.

If you can open BIOS setup by tapping F2 when you boot, look for the Video settings and make sure the Primary Video option is correctly set to use the NVidia card, and disable the Multiple Display option. Be sure to save the changes, if any, before exiting setup..

Can you remove the add-in video card and connect the monitor to an onboard DP?

Do you have the latest NVidia driver installed?

You shouldn't be changing boot order in BIOS. First in the boot sequence should always be Windows Boot Manager. If you want to boot from DVD or USB, use the F12 menu to select the option. Note: A bootable DVD has to be in the drive before you power on, or a bootable USB has to be connected before you power on.

Thanks.

1) I have used this monitor extensively on a different desktop (am in fact using it at present) with no issue whatsoever.

2)  Monitor is correctly set.

3) Sorry, it is indeed the GTX 1660 Ti Dell OEM.

4) I have modified the Primary Video to NVIDIA from Auto and disabled the Multiple Display as you recommended.

5) I would prefer not to remove the card for the moment as the machine is still under warranty and am anxious to avoid any potential problems by removing components myself while this issue is still pending.

6) Windows is indicating the driver verios is from 11/12/20 and is best available.   I will need to check later with Nvidia to be sure.

@Pwalker21   There's no warranty issues if you remove the NVidia video card and then reinstall it, as long as you don't do any damage. And if it is the video card, removing it is the only way to find out. Just swapping motherboards and drives over and over again is a waste of time.

The NVidia driver I linked from Dell was released in 2-2021, so it's relatively new, and I'd install this one...

Does the monitor have its own driver and is the latest version of that driver installed on the XPS 8940?

Have you tried using HDMI instead of DP?

Re: I have not recently tried to boot from a DVD or USB installation media as it seemed easier and faster to just reinstall from the tools available at F12.

It would suggest that the factory installation of Windows 10 on your pc including some Dell bloatware is somehow problematic in your system and causes issue repeatedly, as you have experienced and tried again and again.  At this point I would again suggest try a fresh clean install using installation media tool downloaded directly from Microsoft.  It is quite easy and fast too.  If that solves the issue then you have a more stable and lasting solution.

Thanks.

Prior to posting my question that was indeed my "hunch" as to the underlying problem.  What left me uncertain was I speculated that such a problem would likely be a "known issue" rather than a problem unique to my machine which is entirely standard Dell.

I will go ahead and do what you suggest next because, as a minimum, it will provide a clear baseline for further diagnosis if the becomes necessary.

The only other thing I had thought might be a possibility is some uncommon intermittent electrical problem that occurs in the power down cycle.  I have no idea how to test for that and imagine it is far beyond my abilities.

Thanks.

I agree that there is no issue with the warranty unless there is user damage but Dell advised me not to remove any components myself during the warranty period.  Since the process is simple I would be very comfortable doing it but I did not want to create any situation in which user error might be assigned to me.

On the driver, what I was reporting is the driver that is currently installed after the latest reinstallation of Windows.  When the motherboard and hard drive were replaced I was fairly careful to ensure I had the latest drivers for everything installed.  Thus I think, but cannot be certain, that the Nvidia card did in fact have the driver you referenced at the time of the lastest failure.  It is just that it has not been reinstalled since I have just a basic configuration at the moment to try to test the machine while searching for the cause of the repeated failures.

The monitor has its own driver and is up to date.    The monitor works perfectly with other machines so I think it is not too likely the problem is there.

I have not tried HDMI yet but it is on my list to thinks to check.

Black screen of death is quite common.

If the storage is SSD and not optimized that's where the issue is coming from. In other words if you disconnect the hard drive it will show an error on the screen.

@Pwalker21  - I have a Dell NVidia GTX 1660Ti in my XPS 8930 and Windows Update installed NVidia drive v27.21.14.6137 on 3-25-21. It's listed on the Win 10 View Driver Update History>Driver Updates.

And if no NVidia updates are listed there, you can always check the NVidia driver version in Device Manager.

BTW: What happens if you boot PC in Safe Mode?