Hi, the first thing to do is to have the car scanned for fault codes. The codes will give a technician a good indication as to what the problem is. From your description it sounds like you may have a mass air flow sensor going bad. The sensor is responsible for reading the amount of incoming air into the motor and reporting it to the engine control module so that it can add the appropriate amount of fuel. When the sensor misreads the amount of air it throws your fuel mixture off and results in the hesitation problem.
and this happens only at low speeds? drove fine on the highway with no hesitation , but would stall pulling away at a green light!
Yes, a bad mass air flow sensor would make the most sense and is the most common problem we see for driveability problems but there may be something else going on also. Your fault codes will tell you a lot about the problem. If you have fuel trim fault codes set it will most likely be a bad sensor.