I have a 100 amp service disconnect and a 200 amp main box the 200amp breaker keeps triping but not the 100amp at the pole what could cause this it has been this way for 5 years now and just started doing this thanks

Since the 200 amp CB is tripping, and is downstream of the 100 Amp Main CB, overload is not the issue.

There most likely is a loose connection at or near the 200 Amp CB. A loose connection will cause heat, the heat will be conducted through the metal into the CB causing the thermal device inside the CB to react, and trip.

I once found a nut bolting the CB tab on the load side of a 200 amp breaker, with only a 20 (twenty) amp load, caused enough heat to trip the 200 Amp CB. I was only able to find this loose connection with an Infrared heat detector.

Without having a detector handy, you may try tightening any and all connections. Ideally, the process is to loosen any connection, an then tighten to the proper torque specifications. Over-tightening can be as worse, and at times worse that a loose connection.