Acer Aspire 5742 Problem Please Help!

I have an acer 5742 for about 1 year and a half and yesterday it was on the table and I wasn't doing anything. Suddenly it turned off and the restarted continuosly after 2-3 seconds when it turned on. Can anyone tell me what might have caused this? Or what is happening? I tried pressing power button for 10 sec- 1 min without Ac charger and battery plug it in and so on. Didn't work. The laptop does that if I put the battery and attempt to turn it on it restarts and does that iswell without battery but ac cord pluged in. I have a ling with video on the issue so you can understand better. Any help is highly appreciated. Many thanks

http://www.youtube.com/watch?v=Ci69uv4hyWU