I have a 2000 and a 2002 S2 and i dont know if its coinsidence or not but both of them have a sticking break feel to them, like the piston in the caliper wont release. I put the car in neutral and just tried to push it to see if it would roll like normal, and it felt almost stuck. Is this a common problem, do the rear break rotors lock up easy, or maybe the parking break need to be adjusted? Either or if you have any helpful info I would appreciate it.

 

It's not a bad idea from time to time to pull off the tires and service the brakes. Regrease sliders and use a metal brush to clean off any rust.

Atleast looking at it might give you an idea on whats happening and a solution to your problem.

Oh yeah, check your brake fluid first

 

I'm having a squealing issue now. Seems that my calipers are sticking too. I'd follow what iDomN8U said and check fluids first.