I too would guess faulty PSU as overheating usually doesn't come back on by itself after a minute or two. Still it would have been polite to have answered the questions about how the system was not overheating were determined.
OP had stated that the settings were reverted and that it was working fine for 8 months. There wouldn't be much of a overheating issue unless there was a catastrophic failure heat sink assembly or the computer is dusty as all hell or in a place where it can't breath. Also Intel parts are kind of resilient to catastrophic failures anyway. I've had plenty of CPUs go to 90C because of a botched heat sink install and if it's still relevant, this video https://www.youtube.com/watch?v=y39D4529FM4
(disregarding any sort of flak that Tom's did on the AMD side).
As far as the power supply not responding for some time after shutting down, I've had power supplies do this on me and it was not because of overheating. Even if it was, then that means the power supply is failing and OP should replace it anyway.