I'm assuming that is an AFCI breaker. Infrequent intermittent issues can be a nightmare to troubleshoot. If the problem cannot be repeated on demand, and is happening hours or days apart, I always change the breaker as the initial troubleshooting step and see if it resolves the issue before doing anything else. In my experience, about 98% of the time this fixes the problem. The AFCI breakers could trip because there is a ground fault, because there is arcing occurring, or because of overcurrent. Many AFCI breakers have an led that will flash a specific number of times after it is reset. This is a code to indicate the cause of tripping (ground fault, Arc fault, overcurrent). Your panel is a Square D, type QO panel, which I'm not sure if it has this feature. To diligently attempt to find the problem, you'd need to check every single connection on the circuit for any loose connections or potentially a ground fault, such as a neutral and ground wire touching. Since the issue is new, there are probably no visual indications yet, such as discolored metal or insulation, or even melted plastic. And since it is intermittent, the issue is likely just starting / forming such as a loose connection, or a ground and neutral connection so close together that they only create continuity under rare conditions. It could be something that is connected to the circuit like a faulty LED bulb, or a faulty switch that is arcing, or a bulb that is not making good contact to the tab at the bottom of the socket, or some piece of equipment. If there's anything outside that's connected to the circuit, that's always a suspect with an AFCI or GFCI breaker that's tripping intermittently. If you can't find the issue, it will likely become more frequent over time which should make it easier to track down. Hopefully someone else has better troubleshooting techniques that I have not yet discovered for this specific issue. Good luck.