I have a problem with an electrical circuit in my house. I have a
circuit where the breaker trips repeatedly, but not immediately when I
flip it back on. What I mean is this; I see that the breaker has
tripped, so I flip it back on. After 4 or 5 minutes, the breaker is
invariably trip again. It never trips immediately, but there is that
gap of time between when I turn it on and it trips.

The circuit is barely loaded. Straight from the breaker is an outlet
in the garage (where I usually plug in my water softener but I don't
have one at the moment). From there, the wire goes outside and is
buried all the way to a shed. I have enclosed the buried wired in that
grey conduit all the way from the outside of the house into the shed.
In the shed, I have four outlets (with rarely anything plugged in
unless I'm weed-whacking or something) and four switches going to four
lights. That's it.

I've wondered (and dread) that there's a short somewhere in the outside
part of the wire but I don't know why the breaker wouldn't trip
immediately after I flip it back on. Could it be the breaker is no
good. Any thoughts on the best way I could begin testing where the
problem is?

Thanks in advance for any advice. I greatly appreciate anyone's help!

Greg