1996 Lincoln Continental ENGINE REVS UP TO 4000 RPMS AS SOO

I HAVE A 1996 LINCOLN CONTINENTAL 136,000 MILES. TODAY WHEN I WENT TO WORK I NOTICED THAT AS SOON AS I STARTED THE ENGINE IT REVED UP TO 4000 RPM'S, THEN SLOWED DOWN TO 2000 RPM'S AFTER 3 MINUTES. ALSO WHEN I TURN OFF THE IGNITION AFTER IT REVS UP TO 4000 RPM'S AND TURN IT BACK ON IT REVS TO 2000 RPM'S. I HAVE HAD THIS CAR FOR 11 MONTHS NOW AND THIS IS THE FIRST TIME THAT THIS HAS HAPPENED. IT DRIVES FINE AFTER IT GOES FROM 4000 RPM'S TO 2000 RPM'S.
WHAT DO I NEED TO DO? DOES IT SOUND LIKE MAYBE MY THROTTLE IS STICKING??

PLEASE HELP