Sounds like a worn breaker
Most breakers aren't designed to be used as switches... so tripping breakers on purpose to turn off vampire loads (like the microwave clock) is using up a limited number of lifetime cycles that breaker was designed for. Pennies saved will cost dollars down the road when it's time to buy a new breaker.
The 5 watts or so that microwave clock uses:
8.3 days to use 1 kilowatt-hour of energy.
So that's 44 kilowatt-hours used in 365 days. Assuming worst case of 25 cents/kwh, the microwave clock costs $11/year to run.
I guess $11 isn't pennies, but it isn't a princely sum either. That's one fast food visit, or a fancy coffee.