You need to adjust the view settings regarding motion to suit your needs. You can lock the view to car or horizon or somewhere in between. It's a holdover from P Cars and the amount of complaints about the shakey cam go back to the initial release, and they have sorted it to a degree. By turning legacy on (to 1) and putting the percentage figure to 0 or very low, you lock the view to car - the world shakes with motion forces. 100 will lock to horizon - the car shakes. Turning legacy off and adjusting the percentage figure smooths out the bumps and shaking. It's not perfect, but all games do this to some degree, rf2 for instance, is really hard to dial out all the camera movement even with everything zeroed out.