Hesitation from a stop

My car drives fine, starts fine, but in town traffic makes it hesitates from a stop, like I have to pump the pedal for it to kick in to go. This does not last long maybe three seconds. No lights come on. We have checked the fuel fuses. The air mass sensor plug in. We put fuel additive in case there is junk In the tank. It does not do it at high speeds or constant movement. Only at stop lights and not all the time. My fiance can drive it rev it up to try to get it to do it and it will not do it. I drive slow and easy and it did it three times tonight. We are thinking it is the throttle body, but I am also thinking maybe the air mass sensor. I have tried popping it into second to see if it still does it and it does.

We have checked the air mass sensor just the plug it did not appear dirty. We changed the oil added coolant. It had a transmission flush in may. It has thrown the p0420 code a few times but I turn it off and it stays off for six to eight months and drives fine. No lights appear when it stalls no over heating nothing. However, tonight I did notice after it did it my dash lights were dimmer. Battery was replaced in May as well. And new battery connectors were added last month. If it was a sensor failing I would think the light would come on. I have also looked up fuel pump failure says overheating is a sign mine does not do that. Some days it drives great other days it does not. This morning it ran great to work tonight not so much.