With PSU issues your system wouldn’t be able to boot up. Or if there was some sort of load issue in the middle of usage you’d just see your computer turn off / restart.

What you’re describing is some sort of software or driver problem.

Unlikely. Power supplies usually have internal protection, and as a result, if they become overloaded, they will trip off (and the whole computer either shuts down or reboots). Is it possible the internal protection is not working? Maybe. But it is far more likely the issue is with other hardware, or even more likely, with software/device driver issues. Try booting a LiveCD/LiveUSB with Linux on it or something and see if the problem goes away.

A bad PSU will usually result in boot problems or general instability - applications or OS crashing, bsod etc particularly when power demand spikes (gaming, heavy disk use etc).

Assuming you’re not running out of RAM, this sounds like a software issue. It could be drivers as others mentioned, some background software interfering or perhaps even malware. As a just in case: have you fiddled with process priorities in task manager?

If you’ve got a spare hdd, you could swap that in and do a clean install of your OS. If the issues remain, it’s a hardware problem, if they disappear then it’s something software or config in your current install

When my PSU was going bad, it would shut off when I tried to run high-intensity programs like games.

When my power supply wasn’t enough it would just turn on for like a second then die before the monitor could pick up a signal.

You’d see fireworks

a blue flash, a pop, a wisp of smoke, and then your computer never turns on again