It came to me suddenly this morning, as I was eating breakfast, exactly why the landowner wants to sell the magic mountain and have it moved off his land. (This is in the novel that's my current WIP.) Yesterday I got a whole new novel setting and characters, all in a rush (as if I want any more novels in the To Be Written Queue!). I seem to be having a flurry of ideas again. I usually notice this in the spring, after a long fallow period during the winter, but this seems to be an autumn inspiration.
The spring period of story inspiration is a regular event I've noticed for years, so perhaps it's something to do with day length around the equinoxes?