A/C breaker keeps kicking off on 1st night of camping

I agree with replacing the breaker. Our A/C 20 amp breaker started tripping several years ago. Reset and it would trip again several minutes later. After trailer cooled down it was fine until we traveled to a new location, trailer had heated up, and would start tripping again. Replaced breaker and has never tripped again. They can get weak. Easy and inexpensive to replace. Pull the old one and take it to a home improvement, hardware, or electrical supply store to get the correct form breaker.