2006 Chevy Cobalt HESITATION WHEN PULLING OUT FROM A STOP

Recently I purchased a 2006 Chevy Cobalt (lovely car)and drives well except for something that I'm not sure is even a problem. I don't drive the car a lot or on long distances but occasionally after stopping the car and pushing down on the gas peddle it acts like it doesn't want to go. It always does, however, and rides fine. The previous owner put 29,000 miles on in two years and went back to the dealer for oil changes, etc. And there was no listing of any problems. The car is certified and has 4 year warranty but I feel silly taking it back because it doesn't always happen when I pull out. Also, the car doesn't seem that good on gas too me. Any ideas or is this my imagination. Thanks.