Tonight while cooking supper, the circuit breaker for the microwave's circuit (20 amp) tripped. I reset it, restarted the microwave, and it tripped again in just a few seconds. After dinner, I plugged it in to a different circuit and it worked fine. So I plugged it back into it's original receptacle, and it still worked fine. It has been in the same receptacle for years, and there's not much else on that circuit.
Is this a symptom that the oven is past its prime? Or should I look closer at the circuit breaker? Or is it maybe just one of those things that will never happen again?