If your microwave is not turning on, or if it is turning off by itself, it could have overheated. When a microwave has been in use for a long time and overheats, just give it 30 minutes to cool off and then try to use it again. Otherwise, you'll need to check the light, the ...
The tripping of the circuit breaker could be caused by a problem with the electrical portion of the microwave, or it could be caused by a weak circuit breaker. It is recommended to have the outlet and breaker checked. If this does not resolve the matter, then the unit may require service...