The question must of sounded odd, but there is a point to it!
I also had a similar problem a while back, which turned out to be (very) loose spokes in the rear wheel which flexed because of my weight (310+lbs) giving the whole drive-train a spongy feeling when I started to pedal after freewheeling. It kinda felt like I had a spring between the rear gears and the wheel rim which had to flex slightly in order for the power to be transmitted to the rear wheel. It's kinda hard to put it down in words and I finally figured it out when I had my previous wheels correctly tensioned and could instantly tell when the spokes needed tensioning again because of the springy/sponginess.