A customer is complaining that their laptop often restarts with no warning, most often when they are playing video games or have several programs running at once. What is most likely the issue?
Any computer can overheat, but laptops are compact and can easily overheat when the processor is stressed for long periods of time. Typically when a computer becomes too hot it will simply shut off without warning to prevent any physical damage to the computer.
Wikipedia
Overheating is a phenomenon of rising temperatures in an electrical circuit. Overheating causes damage to the circuit components and can cause fire, explosion, and injury. Damage caused by overheating is usually irreversible; the only way to repair it is to replace some components.