I have had problems with my neck getting stiff and the back of my head becoming very sensitive to the least little bump (the headrest nearly drove me insane cause the slightest little pressure caused head pain). It took me a day for the headache to lessen after last long car trip

In the future I am going to try sitting more forward so my head does not touch the headrest and I am going to be more proactive and take Advil before I get in the car as that seemed to help me