I WAS DRIVING MY 2019 MODEL S TESLA ON AUTOPILOT DOWN THE FREEWAY AT FREEWAY SPEED WHEN SUDDENLY IT STARTED BRAKING AND THE ALARMS WENT OFF AS IF REACTING TO AN IMPENDING COLLISION. ONLY, THERE WAS NOTHING IN FRONT OF ME TO REACT TO. THE GUY BEHIND ME REAR ENDED ME AND SPUN ACROSS TRAFFIC LANES. THANKFULLY, EVERYONE WALKED AWAY FROM THIS WITH WHAT WE THINK IS JUST WHIPLASH AT THIS TIME - IT COULD HAVE BEEN SO MUCH WORSE!