Windows 10: My Pc crashes, no BSOD and restarts the next instant

Hello i keep having an Isue with my Windows 11 Desktop for a while now and i cant find whats wrong.Whenever i play a game and try to watch something else like a Youtube Video or a Twitch Stream after some time, cant say clearly, sometimes after a few minutes, sometimes after an hour or longermy Pc just turns off, as if losing Power, but starts booting up by itself just a moment later,I'm pretty sure the Problem started when i got a new Monitor, its a 1440p Display with flipped Portrait layoutThe Problem also persisted through multiple GPU Driver Updates and Bios updatesI have already switche

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Instant random computer restarts

Ah, got it, just had to go deeper.

 

Pc crashing - black screen with inverted colours, attached a crash log file

Hi,

I have performed all the steps above.

Still no luck, PC hard crashing after playing games like diablo 4 and destiny 2. Quick BSOD and then instant restart.

System scans showed no corruptions on the memory.

 

PC reboots (no BSOD) on CPU stress

Hi fellow TPU members,

not too long ago, the box my gf's PC was transported in gave way on the stairs. Yes, you got it right, that sent a PC tumbling down a flight of steps alright.

Stuff broke. Also, stuff remained intact somehow.

I bought her a new case, new CPU cooler and we removed the floppy drive, so far so good. But the PC started crashing for no apparent reason, without a BSOD.

I tested:

• Memtest86+, left overnight, 0 errors
• Scanned the HDD for errors, nothing there
• Left FurMark burning up the GFX card and drawing some power, no problems there
• Ran Ubuntu from a Live CD doing nothing special, didn't crash
• Ran OCCT, Linpack, Prime95, all 3 caused reboots within minutes
• Oh, and I disabled "Restart on error" so I'm sure it's not a BSOD.

Now, I can still try and test something CPU intensive on Ubuntu, but my guess is the CPU didn't survive.
Before I do anything drastic like whippin' out the magic wallet and get her a new AMD quad, is there anything I didn't see?
I'm guessing the motherboard could be borkered as well, but can I check that other than replacing the CPU with a working one?
Any suggestions on which proggies I can use from an Ubuntu Live CD to stress the CPU?