1) replace PSU
2) replace mtrbd.
3) verify system is clean
4) install system monitoring for temps
You offered nothing on what the system is, etc., no details. If this is an OEM type system, any warranty from the likes of Dell, HP, Gateway, use it.
I'm trying to help someone with a problem where their one-year old desktop computer just randomly powers off. The system does not seem to be getting hot. Any thoughts?