MacBook Pro keeps restarting - newbie I recently upgraded my MacBook Pro to Yosemite. Everything was fine ... then suddenly the MacBook Pro does not start up. It boots with some distorted graphics, and then just immediately restarts. 

I tried Recovery by pressing shift key. Command + Shift. Nothing. Same thing...Apple logo..progress bar, grey screen, fan speeds up ... shutdown.

I tried Apple's recommendations. But surprisingly same sequence..


Option-Command-P-R -- It did give me sound twice and above sequence
repeats. (I don't see those icon etc for hardware test..why ?)
Pressed shift, same sequence repeats.
Command V Video here ... no error but same sequence ... it shows grey
screen and restarts.
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.)