What to do with bootloop on a computer?

Question

Computers

Good afternoon. Very strange things are happening to my computer, and I would need your help.

Components to start:
Motherboard - Asrock AM4 B450 Pro4
RAM - Kingston HyperX Fury Black CL15 8192MBx2
Power Supply - Be Quiet SYSTEM POWER 9 700W
Processor - AMD Ryzen 5 3600
Video Card - RTX 2070 Super 8GB
Solid State Drive - M.2 2280 1Tb Samsung 970 EVO Plus

It all started with the fact that the computer occasionally turned off the image on my two monitors by itself, while the sounds of the system continued to go to the headphones. Sometimes this was accompanied by a very loud hum from the hull. It worked after a reboot.

Then the day before yesterday I played for several hours, no incidents. I closed all games and opened a text editor - the computer turned off by itself and continued to turn off after a minute or two after starting the operating system.

Something similar has already happened with this computer, and last time I got rid of problems after setting up the BIOS: I set either UEFI Only or Legacy Only (unfortunately, I don’t remember exactly), and also changed the CPU Clock from Auto to Manual. I tweaked these two settings, and then the computer stopped letting me past the motherboard logo - it rebooted every time. Only occasionally was it possible to sit for no more than a minute in a running operating system.

I managed to look at the event log, but didn't find anything interesting there - Event ID was 6008, an unexpected shutdown with no useful details.

The first suspicion was that it was time for the motherboard to rest, and I took a new one, Gigabyte AM4 B450M DS3H. I collected everything on it, but it did not give any effect, including after jerking the settings in the BIOS.

The next suspect is the power supply. I took a precisely working 600W PSU from another computer, also put in a weaker video card with which he works every day - no effect.

Since there are two RAM sticks, I thought that one of them could die. The slots for them are working (since the motherboard is new), so I just tried to start up first with only one, then only with the second. Again, no success.

Finally, I thought that the problem might be with the M.2 drive that Windows is booting from. I took a flash drive with Windows, which I wrote down with the official Microsoft utility, and tried to boot from it - rebooting in a minute, even on a flash drive.

Out of desperation, I also tried disabling M.2 and booting from another computer's hard drive. Naturally, no change.

At the moment, I am not able to check only the processor and RAM (although the problem is only if both dice died at the same time). I still came to the conclusion that this is a matter of properly setting the bios, but, to be honest, I ran out of ideas.
I will be glad for any help.