Has the heat sink/cooling fan been cleaned recently?
Just last week, mouse freezing requiring a reboot, or sudden random reboots every few minutes started occurring. I was puzzling over what it could be when the light bulb went on - it's overheating
A thorough cleaning of all the cooling hardware fans/vents/slots, a fresh bead of thermal grease and problem solved.
I was surprised when my tech-guy told me how often common PC issues are caused by lack of attention to cooling elements.
Warning, do not open your PC case if you don't know what you are doing. Take it to a shop for a cleaning.