Rear Brake issue

[chandlerbingfl]

I recently had a local shop replace the rear tire and the tech "adjusted" the rear brakes. I really had no issue with the
brakes other than to have him inspect the pads and hardware and when he was finished I was told everything looked good. In the 3 weeks or so of replacing the rear tire I noticed that every once in a while when I use the rear brake it has a tendency to "grab" almost like I stabbed at the brake pedal. This only last momentarily then the brakes work normally. This has happened a few times but other than that braking (rear) feel fine.

What might cause this "grabbing". Unfortunately the shop where I had the tire replaced / brakes adjusted is now out of business....

Thanks for your input!
chandlerbing