What happens to your body as a car stops and starts?

What happens to your body as a car stops and starts?
Newton's Law:
First law: Whenviewed in aninertial reference frame, an object either is at restor moves at a constant velocity, unless acted upon by an externalforce.
Second law: Theacceleration of a body is directly proportional to, and in the samedirection as, the net force acting on the body, and inverselyproportional to its mass. Thus, F =ma, where F is the netforce acting on the object, m is the mass of the objectand a is the acceleration of the object.Third law: Whenone body exerts a force on a second body, the second bodysimultaneously exerts a force equal in magnitude and opposite indirection to that of the first body.