My dryer is about 11 years old and when I dry my clothes

could be dry motor bearings, or possibly a partial shorted heating element to case ground,next time its running keep track of how warm the breaker gets while its drying, also possible the breaker could be weak from earlier tripouts and just needs replacement,if you can find someone with a clampmeter and monitor the current draw while its drying and see if it starts to draw excessive current at some point