Try making sure there is no way what so ever that the computer can try to access the internet and then turn it on. This is done just in case it was an update that went wrong, the computer will keep trying to redo the update as long as it has internet access. Leaving your running in frustrating circles.
If this doesn't help, then it may well be your hard drive that is going and causing the problem. In that case you would have to check the disk.
NOTE: If the laptop is still under warranty, I would contact the manufacturer about the problem.