XPS 8940, slow boot and no boot

The first step would be to run diagnostics (F12 immediately at boot) and watch for any errors especially drive errors.

I ran the diagnostics and also the dell tech support helped me update the drivers. Still does the same thing Unfourntetly. 

* List every device and cable plugged into the XPS 8940
* How is the monitor connected to the XPS 8940? Using which cable and ports?

Win 10 or Win 11?

You can try disabling Fast Startup in Windows because there are some Microsoft updates that can't be installed when Fast Startup is enabled. They try to install at boot, but eventually fail and "time out" and that's when PC finally boots.

Since Windows won't attempt to install those updates during a Restart, things work fast and more smoothly than when you boot from a full power-off state.

1. Boot to desktop
2. Open Power & Sleep screen
3. Click Additional power settings
4. Click Change what power buttons do
5. Click Change settings that are currently unavailable
6. UNcheck Turn on Fast Startup
7. Click Save changes
8. Do a full power-off shutdown, not just a restart.
9. Power on and boot

Be patient at #9 because any pending updates should be installed before the PC boots. Once you're back at the desktop, re-enable Fast Startup. Then do another full power-off shutdown and boot. See if that solves the problem.

If the same problem recurs after a day or so, disable Fast Startup again because there may be some additional updates that need to be installed...

I have the following plugged in

Main power cord,Mouse, keyboard, audio, and monitor. 

For the monitor. I think the cable I'm using a mini display cable. 

Windows 10. I have tried disabling the fast start up but it hasn't fixed the problem. 

@Applepen22 

Do you have an add-in video card or only use onboard Intel UHD Graphics?

If you have add-in video card, is monitor connected to the card, not to any onboard Intel Graphics port?

What type video port do you use on PC?

What type video port on monitor?

Which video card do you have?

There's another thread where a new XPS 8940 had a black screen at boot that got fixed by uninstalling all NVidia video and audio drivers (Note: not Realtek audio) and all NVidia GeForce software. Then, without rebooting, install this really old NVidia driver. 

Don't know if that will help your situation, assuming you have an NVidia GPU,l but if you want to try this, be sure to manually set a System Restore point before uninstalled all the Nvidia stuff...

I have the Nvidia Geforce GTX  1660 Ti.

Thought about trying the old NVidia drive I linked?

Two more questions...

1. When did this problem start, or has it been this way from the very beginning?

2. Did you recently update the Realtek audio driver?
Windows Update forced a Realtek driver update on XPS 8930 PCs that causes slow boots and reverting to the prior version fixes the problem. No idea if that's relevant to your issues, but something to keep in mind...

I'll try out the older driver. 

Yeah, it has been an issue since day 1 of unboxing the PC. So I imagine the problem wasn't the Realtek as I didn't update it back then.

Thanks!