These bumps are due to a neck/head sensitivity that results from a whiplash type of injury to the head/neck. I have suffered from this for more than decades.

I find the best way to prevent this is to use the energy absorbing capabilities that the back has. This is best when the head and shoulders are bent forward slightly. If you are in a car, you need to have your upper back not against the seat back. Contact with the seat back with your upper back will transmit these vertical forces.

I learned this technique due to my love of roller coasters. Wooden coasters tend to have lots of vibrations. By sitting with my back away from the seat back, I can continue to enjoy the rougher rides.

I do this when riding in the car and encountering a speed bump. If I notice it in time, I need to do this when driving over depressed manhole covers.

YES, speed bumps are a pain in the neck and otherwise.