Jan Webb wrote the following message:

Does it shut down, or does it just spontaneously reboot, giving you the
"you did not shut down properly" blue screen start up scandisk?

If it is spontaneously rebooting, two things come to mind. Power supply
has gone bad, or video drivers. I'd update the video drivers to the
latest versions, and see if that works. Many times, though, it is a
power supply that is going down the tubes, and is clinging on bit
longer.