brake squeal question
 

I've noticed a brake squeal in the rear of my 2000 Sonata but it only
seems to happen the first couple of times applying the brakes after the
car has been sitting. After driving for a while, the squeal is not
there. The brakes seem to work fine as well.

I'm taking the car in to have it checked just in case but I wanted an
opinion as to whether or not the brakes need maintenance or replacing
or if there is something else like dirt build up that might be the
culprit in this case, since its only when the brakes are applied for
the first or second time after starting.