Diagnosis
This is usually an overheating safety trip. The unit's internal thermal cutoff, a KSD switch, is activating. Often caused by blocked exhaust vents at the back.
How to Fix It
Unplug the unit. Let it cool for an hour. Pull it away from the wall. Vacuum the rear exhaust grille thoroughly. Ensure at least 5 inches of clear space behind it. Clean any grease or debris from the intake vents on the bottom.
If That Didn't Work
The KSD thermal cutoff itself may be faulty and tripping prematurely. It's a small disc usually on the heating element housing. A tech would test it for continuity when cool.
Heads Up
Running it cramped in a corner or under a cabinet is the main cause. It needs airflow. This shutdown protects the wiring and components from heat damage.