That could be the problem ... your CPU is running very warm...when the heat is on in your house at 70 degree...it will cause those temp to raise even higher...your "random" restarts and shutdowns may be the result of the CPU protecting itself from overheating. If you have the PC on the floor or in a cabnit in a desk try to move it on top of the desk or put a fan some where around the pc to see if that solves that issue.