I have an old Windows Vista PC that has started acting up. Normally it is in the sleep mode. Lately when I push the start button the fans start running for 2-3 seconds and then it shuts down. This can happen many times in a row but if I lift one side of the computer case a bit (which lies flat on my table) and let it drop back to the table the impact gets the computer working. All the fans appear to work, the pc battery reads 3.19 volts, the memory was removed and reinstalled. Any suggestions what might be causing the trouble that a violent physical impact temporarily fixes? Thanks for any help!