Maladaptive Daydreaming: where wild minds come to rest
I agree. Anything can, and I can't always predict what will. Sometimes I'm just sitting there lost in 1 DD, and out of the blue I hear a refrain from a song that makes me sad, or catch a glimpse of a face that intrigues me, and I'm ambushed (in a delightful way of course.)
Boredom triggers my daydreams. When I'm bored, and if I can, I daydream.