Subtle Vibration in 03 Cav

What could be the cause of a breif "shudder" when coming from a complete stop? It occurs between releasing the break and applying the accelerator and stops at as soon as the car is in motion. The car idles and accelerates smoothly. This might not be a big deal but I just bought the car and I don't want this to worsen or escillate. :eek7: