1997 BMW 3 SERIES Engine Problems

WHEN I WAS AT A STOP LIGHT, MY ENGINE BEGAN TO ACCELERATE WITH MY FOOT ON THE BRAKE. WHEN THE LIGHT TURNED GREEN THE ENGINE CONTINUED TO REVVE HIGHER. IT DID NOT TAMPER DOWN UNTIL I PUT THE CAR IN NEUTRAL. THE ENGINE CONTINUED TO REVVE WHEN I BEGAN TO DRIVE AGAIN UNTIL I CAME TO MY DESTINATION AND PLACED THE CAR IN PARK AND SHUT THE ENGINE OFF. IT DROVE FINE WITHOUT FURTHER INCIDENT THAT DAY. BEFORE THE INCIDENT I HAD TURNED ON THE A/C. ON TUESDAY (2 DAYS LATER) IT UNINTENTIONALLY ACCELERATED AGAIN AT HIGHER REVOLUTIONS AT THE SAME STOP LIGHT. I REPEATED WHAT I DID BUT THIS INCIDENT, THE CAR DID NOT THROTTLE DOWN. IT WAS AS IF IT WAS IN MANUAL MODE WITH THROTTLE FULLY OPENED. I HAD TO PUT THE CAR IN NEUTRAL THEN PARK. MY DESTINATION AT BOTH TIMES WAS 10 MIN AWAY. IT...