My powerbook will not start up all the way. It suddenly went off yesterday and did not give any noticeable warning. I left it alone after trying to start it up several times. I tried again today and had the same problem. I will here the motor for a few seconds and then nothing. Also, it did come on twice, went off both times when titled the entire laptop up. So, if I tilt it at anytime it automatically shut off. Any ideas as of the problem?