MY 2004 BMW 325XI SEDAN WAS ABOUT TO CAREFULLY BACK INTO A SERVICE BAY FROM JUST OUTSIDE THE GARAGE DOOR. AWARE OF THE NEED FOR PRECISION AND CARE (THERE WERE PEOPLE AND ITEMS NEAR THE BAY), I SHIFTED INTO REVERSE, THEN VERY GENTLY STEPPED ON THE ACCELERATOR PEDAL. THERE WAS A MOMENTARY HESITATION, THEN THE CAR BEGAN TO GO BACKWARD SLOWLY FOR ABOUT A HALF SECOND AND THEN, WITHOUT ANY ACTION ON MY PART, THE ENGINE SUDDENLY ROARED TO LIFE AND THE CAR WENT BACKWARDS AT TREMENDOUS SPEED. WITHIN ABOUT TWO SECONDS IT HAD GONE BACK SOME 40+ FEET AND, BECAUSE I HAD TURNED THE WHEEL A BIT BEFORE MOVING THE CAR, THE REAR PIVOTED ALMOST 90 DEGREES AND RAN INTO A GARAGE SIDE WALL ANOTHER 40 OR SO FEET AWAY. AN EMPLOYEE MAY HAVE BEEN BRUSHED AS THE CAR HIT THE WALL NEAR HIM. THE EVENT HAPPENED SO QUICKLY AND UNEXPECTEDLY THAT I HAD NO TIME TO EVEN STEP ON THE BRAKE. I AM A SKILLED DRIVER AND AT NO TIME DID I STEP HARD ON THE ACCELERATOR PEDAL. MAJOR DAMAGE TO TRUNK, REAR PANEL AND TWO DOORS OCCURRED. IN MY CA 50 YEARS OF DRIVING I HAVE HAD ONLY ONE PREVIOUS ACCIDENT. THAT WAS IN FEBRUARY 2007 WHEN, AS I SHIFTED INTO REVERSE IN AN ICY PARKING LOT, A GENTLE PUSH ON THE ACCELERATOR RESULTED IN A SUDDEN RACING OF THE ENGINE AND RESULTED IN VERY RAPID BACKWARD RUSH OF THE CAR. IT HIT A BRICK WALL BEHIND IT AND RESULTED IN MAJOR REAR END DAMAGE. IT WAS THE VERY SAME CAR AS IN THE 2009 ACCIDENT DESCRIBED ABOVE. THE 2007 EVENT WAS ATTRIBUTED TO ICE ON THE PAVEMENT AND NOT FURTHER INVESTIGATE