shimmy at slow speed

I've got a 2000 hyundai elantra that has recently developed a shimmy at between 25-35 mph. It is something that you can feel in the steering wheel, but not the ride. It goes away at higher speeds. Any guesses as to the cause? I'm thinking possible bad tires. I doubt warped rotors because their isn't a bad pulse when braking. Thanks.

Pecos