Do you mean you have your foot on the brake, you shift to reverse and when you take your foot off the brake it still takes about a second or so before the car moves? With any car, as soon as you shift it into gear, you should kinda feel it want to go as soon as the brake is released. If yours isnt, the case, just bring it in to be looked at. It should still be under warranty.
Should be mentioned that if this is happening while parked on an incline, the vehicles "hill-assist" feature will activate making this experience "NORMAL." Never going to hurt to take it to dealer to be checked out though if this occurs on flat surface.