Grey/ black screen of death

I have an issue that occurs very sporadically on my self-built Windows 11 computer.

I can hear the windows "ping", and OS seems to be loading like normal but there is no image on the monitor - only a neutral grey.
Ctrl+Alt+Del gives me a black screen, but nothing more. If I press escape I'm back to the grey screen. Sometimes the grey color is more of a windows-blue.
The only thing I can do is hold the power-button down to force the computer to shut down. When I reboot I'm unable to get into the bios, the post-screen is not showing, and the windows loading-circle is not displaying. Then it is back to the grey/black screen.

Win+Ctrl+Shift+B gives me a "ping" and the screen flashing grey and black, but no more.
My solution is to force the computer off several times until the windows repair-tool starts, and then it can finally boot into windows again.

The computer is very stable otherwise, both during normal office use, gaming and other tasks.

Event Viewer and Reliability Monitor shows the same critical event every time, and I have no other critical events in the logs.
It reads "Windows was not properly shut down", with the following details: Kernel-Power, Event ID 41.

My setup:
Windows 11 IoT LTSC
ASUS ProArt X870e Creators WiFi
Seasonic 860W Platinum
AMD Ryzen 7 98000x3D
Asus GeForce GTX 4070 Super OC 12GB
Corsair Vengeance DDR5 6000Mhz 64GB
Samsung 990 Pro M.2 2TB SSD
I would really appreciate any help on solving this frustrating issue.