Remember temp problems can be on parts that have no temp sensor or a part that has become heat sensitive. That is now shutting down when it used to tolerate so much.
NEVER DISCOUNT HEAT. Always get in there to make the heatsinks clean, spotless and replace heatsink compounds over a few years old.
Also, don't forget PC details.
The above is my OS with 4GB ram...no temp problems ..no fan problems....no error reports . I'm wondering if the PSU is beginning to fail. Pls provide some directions to trace source of this problem