Another thing to check for is loose connections at the breaker, including the connection to the distribution busbar. Heat from a loose connection can trip a breaker.

If you find no loose connections, listen for sizzling or crackling sounds in the breaker which would indicate internal connections going bad. Try placing the tip of a large screwdriver against the breaker case & then place your ear against the end.

Tom

Few things are harder to put up with than the annoyance of a good example.