2005 Chrysler Sebring vibration at 45 / 50 mph

First identify exactly where you're feeling the shaking, steering wheel, seat, or entire body. Switch the tires front-to-rear, then see if the feel changes. If it does, suspect a tire has a broken belt. A broken belt on a front tire will make the steering wheel oscillate back and forth. If it's on the rear, the seat will feel like it's wobbling sideways.

If there's no change, have your mechanic perform a lateral runout test on the front wheels. That simply means using a dial indicator to measure how much each wheel is moving sideways as it goes around. If runout is excessive, say over.045", the suspects are a bent wheel, a bent hub, or a spot of rust behind the brake rotor that prevents it from sitting flat against the hub. That rust can be aggravated when the wheel is removed because the rotor can flop around, and the rust can break off and get caught behind it.