I have never had a dream about transitioning.
When I was much younger, I had dreams that I believe were memories of past lives. The reason I think that is because they were very different from the way a dream "looks" or is experienced. They seemed more real, like a memory, and they all were recollections of how that life ended. What I find intriguing is that in some, I was female (a high priestess within a society like the Aztec or maybe Mayan culture), in one I was a young boy, and in another an adult male who was piloting a small spaceship. So these were all events during different time periods, or possibly alternate realities. I seemed to be most comfortable as the high priestess, despite the outcome of the dream.
Vivid imagination? Maybe. But I can't shake the feeling that these events really happened.