MacBook Pro keeps restarting - newbie
What is the year and model of your MacBook Pro? There is a known graphics failure in the 2011 models of MacBook Pros that is now leading to a class-action lawsuit .

I would also try resetting just the SMC by pressing Shift+Control+Option+Power button at the same time while the computer is off and plugged into power. (You only reset the PRAM according to the steps you have done above.)