Diagnosis
This is a thermal overload cutoff. The main thermal fuse on the heating element assembly is tripping due to excess heat buildup.
How to Fix It
Let the unit cool completely for at least an hour. Before restarting, vacuum the rear vent grilles thoroughly. Ensure the oven is at least 4 inches from walls and the countertop backsplash. Blocked vents cause overheating.
If That Didn't Work
The thermal fuse is a one-time safety device. If it trips, it must be replaced. It's a small white ceramic cylinder attached to the upper heating element assembly inside the top housing.
Heads Up
This is a critical safety component. Do not attempt to bridge the thermal fuse connections. Replace it with the correct part to prevent a fire hazard.