It is restarting probably because it is getting a bad error and is supposed to try again. Hit F8 when it reboots to see if you can get to the boot menu. You should be able to disable auto restart and then maybe you can see what is going on.
It is probably a device driver of some kind, so do whatever you can to simplify your system. If you have USB devices connected, unplug them. Two monitors, unplug one. Fewest hard drives you can and if it continues, possibly turn off the sound or network adapter or whatever you can in the bios. Video drivers are also a problem on occassion so there is also an option for using low resolution drivers.