My MacBook Pro keeps restarting

OK, here's a question for you. I have a MacBook Pro (early 2011 edition) that I am having issues with. My computer has a problem booting up to start. Sometimes the computer will restart several times before I can finally log in.

Other times, I start the computer, I see the Apple logo with the startup prompt (the spinning "circle"), and then just a white screen. I have already gotten the prompt that "there has been problems starting your computer. Wait for a few minutes or press any key to continue."

Can somebody give me an idea of what is happening?

Thanks!

Anotnio Solis