The Head Restraint (AHR) on the driver’s seat opened, without warning, striking the back of my head with considerable force. I was startled and momentarily dazed, as a result. The vehicle was parked at the time, so no impact or collision was involved. The Head restraint has not been repaired and is available for inspection. I have seen many reports of the same problem with numerous other vehicles. The manufacturers should be responsible for the repairs. Thank you!