2006 Chevy Malibu w/ acceleration hesitation?

I purchased a GM certified used, 2006 Malibu (V6). Recently I've noticed it tends to hesitate when I try to accelerate up around 40 mph. this happens on city streets and when I'm trying to accelerate to get on the highway. Other than that it seems to accelerate smoothly and rides quietly.

Also:
The car is on a 5 year, 100,000 mile powertrain warranty. Should whatever repairs or work that needs to be done on it be covered by this? First time car buyer, here ...