My cats will sometimes move their feet as if they are running while they're asleep and, at other times, it seems that they are experiencing other things in their sleep.
I went several years without any recall of dreaming at night. But then, after an injury and medication I began to dream nightly. Most of them are mundane and not enlightening. What I find disturbing about dreams is that my mind can concoct things while I am unconscious. Even the most pleasant dreams represent a spooky independent activity of my mind acting on its own. I have never researched the science of dreams and never put much stock in amateur interpretations. Dreams such as yours might warrant a safety gate at the stairs if they should progress to actual sleepwalking. I hope that hasn’t happened. Dreams are an interesting phenomena but I'm not aware of much study on how and why they happen.