MBP consistently rebooting and failing to shut-down/restart correctly

[Mac77]

My MBP will consistently stop responding shortly after booting up and then immediately restart. The issue occurs typically after a few programs are launched. Also, when I try to restart or shutdown my mac at other times, (when the previous issue isn't occuring) the mac will appear to shutdown but will actually hang after the screen goes blank. I have to manually shut it down. The front indicator light stays lit and indicates the mac is still powered up and the fan is still running. I have to essentially power down manually to get it to restart.
I'm running the newest version of 10.8.2.
Any help or suggestions would be appreciated.

Thanks