New
#21
Absolutely plus any "dry joints" just try the slot fittings or anything that is soldered to the board - not roughly and if it moves just a fraction then you will have a joint that is not making proper contact and while cool / cold it works ok but the heat expansion provides just that tiny bit enough of a gap to lose contact and them on cooling-off - contact is back again.
If as suggested you have overtightened the fixings for the CPU then - same thing as for dry joints is going to happen