Question PC randomly restarting, but only at home ?

[rnayabed]

My computer has been acting very weird for the past few weeks. It started to restart randomly - regardless of whether it is doing browsing or playing games.
There are also no BSODs shown. I have a dual boot system (Windows 10 + openSUSE TW) and the same issue happens in both.

I tried with a different GPU (GT 1030), still the same issue. I also ran MemTest86 Free and it passed all tests. I turned off XMP, still the same issue.

Thinking it is a PSU problem, I took the PC to the repair shop, where weirdly it showed no signs of problems at all. I ran 30 min Power OCCT test, it showed no issues whatsoever. At home, the PC restarts at the 2-3 minute mark. I thought maybe something is wrong with the wall socket/surge protector/power cable. So, I returned, and connected my brother's PC power cable to mine. The same issue occured again. I tried it in different room, from my brother's and mine's, and still the same issue occurs.
Note that my brother's PC has absolutely no issues.

I do not know what to make out of this. Please help.

PC Specs:
CPU: AMD Ryzen 5 3600. No OC
RAM: 2x 8GB DDR4 3200 MHz HyperX
Mobo: Gigabyte B450M DS3H WIFI
GPU: MSI GTX 1060 6 GB
PSU: Cooler Master MWE 650W 80+ White (~3 years old)

 

[helpstar]

check all connections (unplug and reconnect)
check the drives with its manufacturers´ tools
replace the cmos battery

 

[rnayabed]

check all connections (unplug and reconnect)
check the drives with its manufacturers´ tools
replace the cmos battery

Only the CMOS battery left to replace, I tried everything else.