My CPU will randomly get insanely warm when in idle mode. Temps will rise to 100 and the fan becomes obnoxiously loud, it's usually fixed by 1-2 reboots. This happened once a very long time ago and then went away so I just forgot about it, now it has happened two days in a row however. Any ideas what it could be? My CPU is an i5 2500k overclocked to 4GHz.