shaking ?

may be your rotors need to be turned (smoothed with a lathe). Some auto parts places will do this for you and you can pick them up later in the day. I would recommend that you pick up a set (providing you have the funds) and then take the old set and have them turned. Put them on the shelf in the garage and you'll be set for the next time. This can be caused by heavy braking...my wife is a chronic stop at the last second driver. Would also recommend changing the brake pads when you have rotor repairs done, due to the pads "seat" themselves to the rotor for even wear.