Yup, that's a belt slipping; the sound is from the belt rubbing up against the various places it goes around, which means it's not turning those things efficiently, and it's costing you gas. After a while, as you've noticed, the friction heats the belt, it expands, and the noise stops. Once it has a chance to cool off, and you start the car, the whole thing begins over again. The heating and cooling of the belt is wearing it more rapidly than normal, so it will potentially break pretty soon.

You just need to get it replaced. Better to get it replaced BEFORE it breaks and leaves you stuck by the side of the road somewhere, and (potentially) hits things as it comes off at high speed, possibly breaking whatever it hits. So - I'd get it replaced as soon as you can manage it. Most places that do basic maintenance work can take care of it. The last time I had to have mine done in my 1999 Jeep, the guys at my local tire store did the job - took maybe 90 minutes. Much better than a tow truck :-)

Your car has an automatic belt tensioner. If the belt is slipping it's FAR more likely that the tensioner is bad. Read the two posts below to learn how to diagnose a bad tensioner and a bad belt.

http://ricksfreeautorepairadvice.com/dia...

http://ricksfreeautorepairadvice.com/dia...

Your belts are worn. Replace them. On less expensive cars like the one you have, stuff wears out quicker

99% that it's just the belt. They are a routine "wear" part and should be repaced after "x" miles, or "y" years. If it's never been done, or your don't remember doing it, change it out.

I have a 2006 dodge stratus when I start my car there is loud whining fromt the serpitine belt. When I start driving it will get loud everytime I press the gas petal if I let off the gas it get quiter. And it will stop about 15 to 20 minutes of driving is it just a bad belt or could it be sometging else