This will not fix your problem, but it should stop the auto-rebooting so you can get a better idea of what's going on. Do this: (lifted from a newsgroup article)
Uncheck the Automatically restart on system failure option. You can access this option right clicking My
computer\Advance tab\Startup & recovery\settings.
Ok. once you've done that (and reboot so the change is permanent), when you get a failure, you should get a blue screen that will give you some indication of what the real problem is.
You can also look in your "Event Viewer". Here's a Microsoft article about how to use the Event Viewer.
Event Viewer explained
You want to look at both the "System" and "Application" logs in the Event viewer to see if there's any problems. A Red icon (like a stop sign) will tell you a very serious event has taken place. Yellow icons are "warning" icons...and white icons with an exclamation point are simply "information" icons that tell you that something has taken place.
There's ALWAYS going to be entries in the Event viewer logs, so don't freak out if there's a lot of stuff there. However, you're most interested, as I said, about headings preceeded by a red icon. This will point you to the errors you're having.
Now, once you've made the changes to your settings preventing automatic rebooting, make note of any blue screen error messages you get. Additionally, post any "Stop" errors you see in the Event Viewer, particularly if you notice they've occured at the same time you get the blue screen (they're all timestamped in the Event Viewer).
