Problem with circuit breaker that keeps tripping

[Kyle J.]

I have a double 20-amp circuit breaker where one of the breakers keeps tripping (halfway between the on and off position).  The breaker that's tripping controls 4 outlets on a kitchen island.  One of these outlets is a GFCI that has a Keurig coffee maker plugged into it.  The other 3 outlets are regular outlets that have nothing plugged into them. 

The breaker just started tripping about 3 weeks ago, and has tripped about once a week since then (different days/times).  Each time it tripped, the Keurig coffee maker was plugged in, but not in use.  So obviously it's not drawing a big load.

The house is newer (about 13 years old) and there are no other electrical issues.

I'm normally able to fix most of my own electrical issues, but this problem is baffling me.  I have a couple ideas, but wanted to see if any of the experts out there have an idea of what might be going on???