That mini-dream is called hypnogogic imagery. It happens every time you fall asleep, if you let it play out it may or may not turn into a full dream. Whether it does or doesn't seems arbitrary, but once the imagery goes away do a reality check.

The guy above you's LD counter is at one, asking him what technique he uses is pretty useless No offense. For beginners, DILD and WBTB work the best. But try a WILD anyway. I fail WILD's a lot, but recently I've noticed that while I'm waiting to WILD I'm thinking about lucid dreaming so I end up with a WBTB.