I've got a 2011 Dodge Caliber Mainstreet and during my drive home from work around 3:30am my headrest out of nowhere popped, hitting me in the back of the head and neck. There are 0 warning lights/codes present. I did not make any harsh accelerations or break, nor did I turn wildly. I was already settled into a lane on the highway and had already come to posted speed (60 mph) I was on I-610 West heading home and thankfully there were very few vehicles on the highway. Otherwise I probably would have caused an accident when I swerved out of my lane after being hit rather violently in the back of my head. The sound AND impact startled me not to mention hurt pretty bad and left a pretty good sized goose egg on the back of my head. I managed to make it back home be it the trip between my home and work is only 13 mi. Due to the fact that it was so early in the morning and still dark outside I chose to wait until daylight before I got ready for my next shift to take a look into what could have been the cause as well as checking to see what was needed to remedy the situation. I'm a personal driver for Alto so I know all about harsh events while driving a vehicle and none of which were the case in this instance. This happened completely out of nowhere for no apparent reason and with no warning whatsoever. I honestly wasn't even aware that there was anything in my headrest that could do anything like this. This is very dangerous and upon searching the internet I realize that I'm not th