1996 Pontiac Firebird squealing front disc brakes

1996 Pontiac Firebird mileage: 124,500. Recently I noticed squealing front disc brakes they only squeal with my foot off pedal and if I press brake pedal about a 1/2 in the squeal disappears. I have brakes and they work fine but there is something wrong, the squealing is very loud on the freeway and embarrassing to drive. Sometimes, rarely, it will go away for a few seconds. What is going on and how do I fix the problem?