Randomly BSOD (or shutdown) with BCCode 124

As the title implies, I keep getting random BSOD. I don't really see the blue screen, but my pc just shuts down..

I recently bought a new graphic card and new computers case, transferred all the hardware to the new case and it ran fine for a few days. But then the BSOD occured

I looked up the minidump and it's mainly a BSOD with the BCCode 124. Also, the corrupted file seems to be the ntoskrnl.exe.

The BSOD's are really random.. Sometimes, my pc runs fine for an hour or 6, the other time it occures 3 times in half an hour.. Not doing anything weird, but they usually occure when I'm gone and my pc just does nothing (not playing any music or having a game open)

I'm not really a great expert on pc and hardware so I'm not sure if it's really the hardware or not (I asked a friend (who is an expert on hardware and such) and he is sure the hardware currently in my pc is fine.

I don't know which info you guys need to know what the real problem is, but I did use the diagnostic tool as I was told to!