Q: Re-starting of Mac book pro

What model MacBook Pro?

Could it be this

http://www.apple.com/support/macbookpro-videoissues/

If you are getting a kernel panic

OS X: About kernel panics - Apple Support

Log it

Mac OS X: How to log a kernel panic - Apple Support

and post it here

Otherwise:

• Note the time of the next unintended reboot. After rebooting open the Console app in Finder>Applications>Utilities and look for log entries at the time of the reboot. Post suspicious ones here.

Look before the log entry that starts with BOOT_TIME since that is the first line of a bootup

This is the Mac Pro desktop forum. I requested your post be moved to the MacBook Pro laptop forum.