Have you cleaned the inside of the PC? Is dust clogging cooling fins or fans or
case vents? Are fans spinning? PSUs can overheat and cause breakdown as well.
i don't have such skill as pc maintenance. i have removed heat sink but unable to install back. before that i have tested memory with memtest86+, it quickly shutdown. i think it's not memory's fault, if it is memtest86+ shall report error in red.