What can cause squeaking from my brakes while driving but not while braking?

My car has been squeaking from the brakes (I think) as I’m slowly cruising. Like in a parking ramp. It doesn’t squeak at higher speeds. Also it doesn’t squeak when I brake at all, only while slowly cruising a slight squeak, squeak. I have no clue what condition my brakes are in I had them checked twice. about 6 months ago I was told 10,000 more miles or so. and Then 2 months ago I was told 30,000–40,000. These brakes are probably about 3 years old. Can anyone tell me whats wrong?