[adanthar]

That sounds more and more like a heating problem...30C is very low even for a startup temp, though.

Try putting it on the side (no, you won't damage the HDD/DVD drive/anything else) so that the heatsink faces up, then take off the cover and run a fan off the edge of a table right into the guts of the PC. If it is now normal it's 100% the heatsink and you can replace that. If not, it's probably the RAM/CPU or some combination of the two.