PSU sounds like a good lead for investigation.
Try removing some hardware like the 2 GPUs, leave only one stick of RAM and only one SSD, reset CMOS and see if the PC runs.
If the PSU is failling, it should work a little better providing less power.
Might not be PSU, but worth trying IMHO.
Also, some RAM stick going bad might cause funky behaviors. So, pick one and use the PC, see if runs OK.
Does your board have debug leds? If so, what codes you see?
Other than that, I would start an RMA if still possible.