Circuit breaker for garage has been fine for ten years.Lately it trips at no certain time.Not when opening garage door etc.Will not trip on a regular basis,but when it did I could reset it and it would be fine for a day or sometimes two.No changes in load on breaker for years. Today I reset breaker and I now have no power at all in garage. Replace breaker?
There may be something on that breaker's circuit that is causing it to trip and prevent a fire/short.
What you need to do is find everything that is on that circuit. Afterwards, see if there's anything in any of those objects that could be tripping it. Connections becoming overloaded, being loose or wired improperly could also cause it to trip. Be sure to check that as well.
If you do find something, resolve the issue and reset your breaker.
However, breakers may trip by themselves from old age at times. If it wasn't caused by anything else I mentioned earlier, this may be the cause. You'll need to replace that breaker. If you're not sure how, I recommend you hire a licensed electrician.