Hi Mrs C! People usually dream during REM, rapid eye-movement sleep. (5th sleep stage) They are generally unable to move their muscles (although some people can— hence my husband dances and wrestles in his sleep now and then, not much fun for me, but he also sings a bit of opera occasionally which cracks me up).
When you hit the hay, and you’re already relaxed and sleepy, you might instantly shift into the hypnogogic, dream-like stage. I do this easily too. Pictures, sounds, and even mind-movies in a jumbled state might flow through your mind.
What I described is often associated with narcolepsy, although I don’t have it and my hypnogogic state is vivid and fast — maybe you’re like me.
A friend of mine falls asleep in the day instantly when she gets the urge. Once she fell asleep in the middle of an art exhibition I held. I got her behind the display where she snored away as people looked around. If you don’t do that kind of thing, you probably don’t have narcolepsy!