AMD system frequently crashing while gaming

EDIT 2: The PSU was not the problem. I've ended up sending my GPU back for repair/replacement.

EDIT: Thank you /u/Doootard for the heads-up about transient power spikes, after reinstalling Windows and experiencing the same crashes there I'm pretty sure that that's the issue I'm encountering. Ordered a new PSU!

Hi guys, I'm at my wits' end trying to figure out this problem so I'm finally turning to reddit for help.

Here's my system info from hyfetch

For months now while gaming my entire computer will crash out of the blue. Sometimes the last second or two of audio will replay over and over before everything shuts down, but sometimes it will all just go black very suddenly.

Occasionally the system will fully reboot after one of these crashes, but most of the time it simply shuts down, for a second, then my hardware will fire up again but there'll be no output to my monitors, and I'm forced to shut it down again via the power button.

There doesn't seem to be any pattern to the crashes; I've seen it crash while my GPU is maxxed out at 100% utilisation, but also in less demanding settings where CPU usage is about 10% and the GPU is only around 30%. I've stress tested my CPU, GPU and RAM, but synthetic loads don't seem to trigger crashes, it only happens while I'm actually gaming.

Games I've had this happen in are: World of Warcraft (via Lutris), Overwatch, Baldur's Gate 3, Sekiro, and Monster Hunter Rise (via Steam, native package)

These crashes don't seem to leave any trace in my system logs. Searching through journalctl shows nothing out of the ordinary right before the system powers down.

In my attempts to stop the crashes, I've tried:

None of these have helped at all.

I'd be EXTREMELY grateful if anybody can offer any advice, these crashes are occurring on a daily basis, sometimes multiple times a day, and I'm tearing my hair out trying to figure out the cause.