So I kinda figure it’s either the PSU or one of my hard drives, but what the issue is is that me PC first makes a click sound (as if I physically shut it down), then restarts some time after.
When it restarts it makes a bit noisier click sound, same as the power button switching does.
I have verified it’s not ghosts or little green men. I can’t say for certain about Martians.
It’s just weird. I’ll be unplugging both HDD’s today to see if it goes away. Then one-by-one plug things in/out.
It’s most likely originating from a relay switching inside your PSU. It’s perfectly normal - my Be Quiet unit (slightly ironic, I know) does it and I’ve never had any issues.