Whats going on with my transmission?

Ok, we have a 2006 Chevy Monte Carlo automatic. It shifts fine and smooth just like its supposed to. But, if i put my car from park to drive and press the gas pedal(sometimes i do this pretty qu ick) It is sort of slow to engage and i feel it bump into gear. Same thing for drive to reverse. This dosent happen very often just every now and then. I happened twice today. But it drives fine no hard gear changing or anything