Problem booting computer without tapping it.

Computer worked fine in the morning before I left. I put it too sleep. Got off the train and decided to use it. It wouldn't come on. So I took battery out, put it back in and tried powering it up again. When I did that you heard the computer come on but nothing should on the screen didn't hear the chime all you heard was the fan just blowing did this many times. Finally I tapped the bottom and it booted but then it froze. I took it apart to see if anything is loose but there is nothing and it keeps doing the same thing.