Car won’t shift out of park

I have a 95 Cavalier and it?s been running wonderfully. I drove it all day today around town doing errands.....and no problems. I came home for about 30 minute to eat lunch and when I got in my car to leave again, it wouldn?t shift out of park. It?s an automatic transmission and the actual gear shift will shift into all gears, but it?s not really shifing out of park....the indicator on the dash board shows it?s still in park. Any ideas anyone? I?ve never had any problems with this car and don?t have a mechanic. Could it possibly be a broken belt or something as simple as that? Help from a single,