Now I understand. Since you are using the real power adapter and have the same problem with another adapter, it points almost certainly to a problem with the power circuitry inside the laptop. Most power supplies (I'm talking about inside the laptop) are built with monitoring circuitry such that if one on the power supply output voltages goes out of tolerance, a reset signal is generated. This would cause your machine to restart. Why that is happening I couldn't guess but I would be thinking there is a problem with the motherboard (that is where the internal power supply lives). Sorry I can't be more helpful. Having random restarts is not only annoying but can mess up the system software sometimes (rarely).