My Mac laptop computer is really messed up. I can't get it to totally turn on.

The computer will make a loud tone, give the Apple opening “chord”, and then begin an intermittent scratching-type sound, all while the screen is still black. Then the screen turns white and a “file” shape appears in the middle of the screen. It’s very small. Then, inside the file shape appears an alternating question mark and Finder icon. This continues to happen for about 5 minutes and then, the computer turns itself off. Can anyone out there help me?