squeaking brakes

I bought a 2001 SC2 a few weeks ago with about 30K miles on it. Since then, every time I start up the car, the brakes squeak and grind a little for the first 30 seconds or so of pulling out and driving slow. The squeaking stops once I get going; it only happens when I start driving (and doesn't recur even if I slow down). Can anyone explain this? Are new pads required, or is it something else? Or is this just normal?

Thanks!

Had a Saturn for 5 years & it done that all the time I had it. I was told by Saturn & other people this is due to a thin layer of rust builds up over night or when it damp. After I changed the rotors the fronts quit. I never change the rear drums and they continue to do that. Check the pads and shoes to make sure they are good but @ 30k they should be in good shape. Changed mine @ 50K & they was still good.