Hi sorry for the late reply, i've been troubleshooting for the same issue for a month now.
I've used to let the PSU constantly powered.
I've switched it off only when i had to touch stuff inside the case.
At the moment i've changed RAM, Changed GPU, Recabled everything ( and it seemed to work for an entire day, but then the same problem appeared ), updated bios, now i'll try to reset the CMOS removing the battery.
Tomorrow i'll try a new PSU downgrading from 850w platinum to 650w platinum, i had a faulty 3070 ti and now i've a 3070, should be fine, at least for a test.
Then i've to try to change mobo and the I/O button.
I do not recall exactly when it all started, if it was when i changed PSU or the AIO Pump, i didn't have a proper GPU at the time so i've started using my old 1060 gb.
I've also tested start pc without gpu connected and it had the same problem, not always but sometimes..
Any help it's really appreciated..