Hey OP! have you managed to fix it? i'm having the same problems here. random restarts (when i say random its really random... no patterns) no BSOD...
the thing that managed to fix this was removing my GPU(RX 580 2048sp) from the PCIE slot. i tested the pc with the 8 pin GPU power connector still attached but to no avail, restarted anyways. However, i don't know if it's my gpu that's doing this or if it's possibly my MOBO's PCIE slot.
EDIT: it turns out my gpu was fine, it wasn´t the problem. i´m still facing this issue to this day. what helped a bit was turning off xmp. it didnt solve the issue as it still restarts randomly but it lessened from various times per day to once every few days. i asked some overclocking guys and they say it might be the 5v line in my psu, but i still can't afford a new psu to test. I'll update this if/when i change it.
EDIT 2: SOLVED!!! (for me at least). It really was my power supply. i exchanged it and the problems were gone. I hope this helps others out. BUT, there have been other cases where it was the CPU failing, or other hardware components, is my case it was PSU.