alright, you may have a RAM clash, which
means that you are using 2 different kinds of ram which arent
compatible with each other. or more likely, one of the gold
connectors on your CPU has melted to a point
that there is very little contact between it and once your cpu
reaches a certain temperature, it would melt and disconnect from
each other, but would reconnect after awhile. this may explain why
the computer is shutting down after a stipulated period. hope this
helps