The most common reason a car or vehicle bounces excessively is due to the bad rack and pinion and steering linkage.
When your rack and pinion is going bad it can cause excessive vehicle bouncing and even swaying in your vehicle.
Rack bushings and damage to the steering linkage are also common causes of a vehicle or car to bounce excessively.
If your car just suddenly started bouncing excessively it's a sign of a problem with the rack and pinion or steering linkage that can get worse overtime and could result in loss of control of the vehicle.
I would recommend having a mechanic look at the car and get the problem fixed before it causes you to lose control of the vehicle and possibly get into a wreck that could injure you or your family or even become fatal.