first thing Chris if possible is to get the error code;
If you can boot into safemode;
Right click COMPUTER and select Properties and then Advanced system settings / start and recovery settings / Untick automatically Restart and ok.
Hopefully when you reboot the system,the error code will be displayed,post that back here.
At the moment your problem could be one of many things.
You could try reseating the ram normally located under a flap on the bottom of the laptop.
Another possibility is the laptop has a conflict with a service pack update,so if possible use system restore from safemode.