Computer beeps twice at random times

Hello,


could anyone help me my computer turns on and plays for a couple of hours sometimes and after that it beeps twice it is like it has just been unplugged it just totally switches off and it doesnt restart I have to switch it on for it to work again but sometimes it just dont work at all could it be something with the heat? any help would be appreciated and will be very grateful for anyone to use 5 mins of there time to help out.

thanks all