Is it normal that i had my first erotic dreams in first grade?

I used to have a recurring erotic dream in first and second grade, that involved being strapped down and stimulated by a tentacle machine. Obviously, I was far too young to have discovered porn, though I had already stumbled across masturbation, so this came entirely from my own imagination. In the dreams, I was older than in real life, though I can't remember how much older. Often the dreams took place in an octagon shaped room, and I was strapped down on a raised chair in the centre that was kind of like a dentist chair. I had these dreams at least twice a week, and then they just stopped, one day.