I get almost a pulsing from the steering wheel

When braking from time to time, I get almost a pulsing from the steering wheel (shakes back and forth rapidly). I'm guessing that it's warped rotors, but I don't feel much (if any) vibration through the pedal. Any other idea what it could be? I have never had the wheels rebalanced, but have rotated the tires every 7500 miles. I'm not particularly hard on my brakes. Seems odd it would have warped rotors after only 25000 miles. Are the brakes fastened to the vehicle in an abnormal way? I've done brake jobs on other cars before (Mazda Protege, Pontiac Grand Prix, Chevy Blazer). The pads on the car currently are still pretty thick. I've head of people "buffing" the brake pads. Thoughts on this? How can one buff them? Grinder? Machine shop? I can have a local machine shop turn the rotors for $10 each, so if I can buff the pads, a front brake job will only run me about $20. Any input is appreciated.