try starting up into vga mode or last good configuration
you can get to the options by hitting f8 key when it booting up before the screen with the xp logo
look for when it tells you to do so

is there a code with the cannot display and have you checked the trusted/blocked sites?

also see if you can access it through another browser or something that still uses ie shell like maxthon

ok,
lets see
if you trurn your computer on and not use it does it still restart?
-just turn it on and leave it alone for a few hours

there are a few things that can cause it to happen but...

are there any error meseges or a blue screen?
any beeps out of the norm signs?
does this happen durning certain usage (many programs running, only while playing music/games ... so on)
does it...