The past Few days the microwave would trip the breaker. today I went to use it and it worked for 30 seconds when I checked what I was heating and turned it bakc on and it would not work

Microwaves that are either built in, a part of the oven, or over the range are on a dedicated circuit by law. This means nothing else could have tripped that breaker but the microwave.
If it has a problem severe enough to trip a 20 amp breaker several times, it is only getting worse each time you reset the breaker and turn it on.
There is a possible chance of fire. I recommend you turn the circuit breaker off and replace the microwave. Is it a plug in, or over the range type?

Circuit breakers, like everything else, do fail. It's always possible the circuit breaker may have become weak.

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