Auto breakers may reset with a supply voltage cycle or based on time once they cool down(seconds if the draw returns within limits). Which one depends on the exact model.
Biggest problem with a manual reset is not knowing it cut power and getting pulled over for inop trailer lights or the risk of getting out of the vehicle while on the highway to reset.
If you are just towing a simple trailer, neither route matters because you would never hit that limit without a failure. If you are towing a camper, then I would personally wouldn't care because I would have the whole thing behind a fuse and the power in the camper would be off so only the required lights are going.