If this happens only in the morning the culprit may be moisture in the distributor cap. Why? During the night condensation or moisture can form on the inside of the distributor cap. This is due to cold and wet weather and the fact that the engine is cold. This moisture allows electrical current to arc inside the distributor cap and this arcing causes the engine to misfire.
If this problem has slowly gotten worse over time then a vacuum leak could be the cause. Why? Vacuum leaks typically start out small almost unnoticeable and gradually become worse due to heat and pressure inside the engine. Any leak in a fuel system’s vacuum will intermittently throw off the air/fuel mixture that enters the engines combustion chamber. This results in a hesitation or sometimes, jerking.
If the hesitation has stayed the same over time then you may have a faulty accelerator pump on a carbureted engine. Why? The accelerator pump gives the engine the extra fuel it needs to accelerate smoothly. A faulty accelerator pump will either not work at all or only work intermittently. In either case the result is usually hesitant or jerky acceleration.
If the hesitation has stayed the same over time then you may have a bad throttle position sensor on a fuel injected vehicle. Why? The throttle position sensor measures how far the throttle is open and sends this information to the vehicles computer which in turn calculates the precise amount of fuel to inject into the engine. A faulty throttle position sensor will adversely affect the injection of gas into the engine, often resulting in hesitant or jerky operation.