My Macbook is 1.5 years old (13in, white, 2 GHz). About two weeks ago, it would randomly shut off. It would restart fine, but shut off sooner. Sometimes, it wouldn't even restart. Now, it's at the point where when I power it on, it rarely restarts past the white apple start-up screen. My thought is that it is overheating. Are there any more ideas? What can I do to save my macbook?