I'm no expert but I had a Dell that did the same thing. Got it from a friend who was tired of it going through restart constantly. Issue was he had 3-4 anti-virus programs running at start up and each one was cancelling out the next, so it would begin to start and shut down for an endless loop. Usually a control-F11 or just F11 (depending on your computer) will start it in a safe mode and you may be able to check it from there. I hope it is an easy solution like this.