Q: My car begins a bouncing sensation when braking at higher speeds

Any vibration felt only when the brakes are applied would typically be a brake pulsation. If the brake rotors are warped, you can feel a vibration in different forms depending on which rotors are the issue - front or rear.

If the front rotors are warped, you will typically feel a vibration in the steering wheel when braking. The steering wheel will vibrate back and forth. If the rear rotors are warped, then you will typically feel a vibration in your seat.

Kind of like the rear of the car is wagging back and forth and felt in your seat. If it is bad enough that you feel it in the steering wheel as well as your seat, then you may have warped rotors front and rear. Rotors can warp due to heat, either from being too thin and past their usable service life, or if the brakes are used hard and often.

Whether it is front, rear, or all 4 rotors that are warped, the brake pads should be replaced along with the rotors.