Thanks for replying!
Then I don't understand what the problem could be.
I'm not trying to overclock, it's a non k in a mini itx case after all, I didn't even activate XMP.
Today the system crashed in the same way while playing Rocket League. After reboot it skipped the Asus UEFI and showed me the Megatrends page saying something like "Overclocking failed" and allowed me to get in the UEFI.
I've set everything to default again and computer started.
I really don't know what it could be. I'm sure that temperatures are not a problem, sometimes the hottest core reaches 80+ degrees for a mere second but as soon as I see it I make sure the entire pc cools a little bit before playing again. I'll add another case fan as soon as I can, but again, temperatures should not be the problem.
It really bugs me that "overclocking failed" page I see sometimes, and now I'm scared to fry my pc again, ruining some of the fan of having a new pc that I even built myself...