Microwave is Turning Off

Are the exhaust vents blocked? 

Do not block the exhaust vents or air intake openings. Allow a few inches of space at the back and side of the Microwave Oven where the exhaust vents are located. Blocking the exhaust vents could cause damage to the Microwave Oven as well as poor cooking results.

Make sure the Microwave Oven legs are in place to ensure proper airflow. If vents are blocked, a sensitive thermal device may automatically turn the microwave oven off. Once it has cooled, the microwave oven should work properly.