This does not make any sense, exactly how are you turning it off? The correct way is Gracefully from the Start Button. Many just close the Screen, and that puts the Laptop into a Standby or Hibernation State. Then some do Hard Shut Downs with the Power Button, and that's not good. If you are pressing the Power Button to turn it back on, and nothing is happening for 8 Hours. It sounds like the Power Button is broken, or some connection in the Start Up. It does sound like a Motherboard problem. We do need more information like the Model Number.