Couple of guesses I have:

• potential graphics driver issues
  • s: could try reinstalling/updating graphics drivers
• Microsoft
  • s1: full system refresh via Windows reinstall (after backing up all user files)
  • s2: for beginners; Linux Mint

hard to say what else without any additional info (or having your device in front of me to figure out what's happening)

• for example, did you happen to install anything or was there a recent Windows update?

Obligatory: You should ditch windows and install Linux instead

Now, with that out of the way:
Sounds like a hardware problem. Is this a stationary or a laptop? How have you ruled out overheating? Keep in mind that there are more things than the CPU that can overheat.

Restarting like that, it's either overheating (reaching 100°C) but you ruled out that, so low voltages, maybe some voltage on your PSU is weak, sometimes a 1.3V becoming 1.2V and it reboot.

Sounds like a faulty PSU. I had that happen and it went away as soon as I got a replacement. GPUs can cause power spikes beyond the specifications in the millisecond range, causing the overload protection of the PSU to kick in and shut down the PC. This causes no bluesceen and creates a reboot instead. It's hard to track down because the windows error log can say all sorts of things.

Alternative remove your GPU driver via DDU uninstall tool and clean install it. I also had one system that didn't like TPM enabled, but it's basically requirement for win11, so.

i join in on the PSU chorus. no bluescreen normally means power loss, so either the PSU craps out, or it doesn't get the power. a defect of the mainboard is not completely out of the question tho.

grab yourself the free version of HWInfo64, and check the voltages below, they should be a) stable (and i mean stable - mine do not move at all and i would be concerned if they did) and b) close to the values in the name (12v, 3.3v, 5v). since you have complete power loss, it's probably the 12v.

PSUs do age and lose about 10% of "maximum wattage" where they still stay in tolerance levels per year.

e: even if the voltages seem stable and ok i would still start looking at replacing the PSU if it's old. e2: a classic one would be loose cables tho, either Power Cable or the 12v connector to the mainboard

+1 PSU

Everyone saying PSU, but I also had a similar issue and it turned out to be my GPU overheating (driver did an emergency shutdown of windows.) It was a fair few years old, but after a re-paste of the GPU thermal compound the issue went away. The reason I say is it's probably cheaper than a new PSU, so I would do it first.

My friend had this issue recently, it turned out to be his CPU overheating, his event log also showed no details of the cause, it was only when he installed a temp monitor and kept it open on his 2nd screen that he saw his CPU was hitting the max allowed temp just before getting the power cut.

Hope you manage to get it sorted