WE WERE LEAVING A DINER PARKING LOT IN THE AFTERNOON, WHEN I HAD TO STOP FOR A DELIVERY TRUCK BLOCKING OUR EXIT. WHEN THE TRUCK PULLED FORWARD I LIGHTLY PRESSED THE ACCELERATOR AND THE CAR BEGAN TO SURGE FORWARD AND TO OUR LEFT(MY WIFE WAS IN THE CAR WITH ME). I PRESSED DOWN ON THE BRAKES AND THE CAR CONTINUED FORWARD AND BEGAN TO TURN TO THE RIGHT AND I TRIED TO STEER THE CAR TO THE LEFT BUT THE STEERING DID NOT RESPOND RESULTING IN MY HITTING TWO PARKED CARS. I HAD THE CAR TOWED TO THE CADILLAC DEALER. THE DEALER INDICATED THAT THERE WAS NOTHING WRONG WITH THE CAR AND SUGGESTED THAT THE SURGE WAS CAUSED MY A SECONDARY CAR MAT BUT COULD NOT EXPLAIN THE STEERING PROBLEM. THIS SAME SITUATION OCCURRED DURING OUR SEVERE SNOW STORM LAST WINTER. AT THE TIME I ASSUMED IT WAS DUE TO ICING CONDITIONS ON THE ROAD AND MY DEALER INDICATED THAT THEY HAD RESET THE CAR CODES TO CORRECT ANY ERRORS(STABILITY CONTROL LIGHT STAYED ON)