Incident happened while sitting in the vehicle, diagnosing an issue with the catalytic converter. A loud noise was heard just as something struck me in the back/ side of the head. The result was my head being whipped forward/ sideways and leaving my head/ neck sore, especially when I woke up the next morning. Upon inspection, it was determined that the headrest in the driver seat had “deployed” unprovoked. Upon searching google / nhtsa for this issue I found that there were issues with other models that had extended warranties. I then contacted the vehicle owner and asked if they had received any notice about this issue. Vehicle owner replied that the passenger side headrest had already deployed unexpectedly while driving down the road, almost causing an accident, and was repaired at a dealership in March 2024. Vehicle owner also stated (and sent email proof) that the dealership stated that they “could not replace the driver side headrest if it was not deployed because they would be charged by the manufacturer if they turned in an undeployed headrest.” There were no lights, warnings or indications that the headrest was going to deploy. The vehicle is available for inspection and the headrest has not been repaired.