The lift gate on my vehicle closed suddenly and for no apparent reason as I was loading groceries into the vehicle. The lift gate hit me in the back of the head and did NOT retract/open upon contact. I had to quickly lift the lift gate with both hands to get out of the way and press the button for the lift gate to open. A couple of minutes later, the lift gate again closed suddenly and for no apparent reason; however, I was not hurt the second time and was able to move out of the way and press the button to stop/open the lift gate.