Yes, I sometimes have a [nobabe]wet dream[/nobabe], but not often. I'm way past my 20's, by the way. It seems to be related to how long it's been since the last time I ejaculated, but that's not always the case. Sometimes it's related (I think) to what I've been watching or reading, but not always. They're always erotic dreams, where some sexy girl - maybe someone on TV or someone at my work - enters the dream and we get into sexual activity. As I cum in the dream, I wake up and find my penis pulsing and I'm cumming in real life.
This isn't something that I can make happen - it just happens. I don't worry about it.