By windows page, do you mean the boot loading screen? Your problem may be an overheating issue. Try popping open your case and make sure the processor fan is spinning and not clogged down with dust. You can also check your BIOS and see if your screen shows the temperatures for your processor. You should be running around 75 degrees celsius if I remember correctly and the shutoff point is somewhere around 100 degrees celsius.
Another option I remember from my windows days, if you goto control panel>system>Advanced>Startup and Recovery>Settings>From here, uncheck the box that says "Automatically restart". If your computer is experiencing a serious error upon booting, this would explain the rebooting. If this fixes the solution, check your windows error log and see what the culprit is.
Hopefully one of these two ideas fixes your problem, if not get back and keep us updated. - Sub