I had just parked my vehicle in my drive and turned it off. I opened my door then sat back in my seat to stretch my back, sitting straight up with my head against the headrest, before getting out. As soon as I leaned my head against the headrest it, for lack of better terms, exploded into the back of my head. It hit me with such force I was not sure what had happened as there was nobody around me that couldâve cause it. Sure enough there was no accident to cause it. I have had a headache and back pain for a week due to it.