I do this all the time. Its called "Chaining"

I basically go to sleep and when i wake in the middle of the night for a couple of seconds i dont move and i visualize myself back in the dream i just awoke from and after a fews seconds the dream absorbs me, and now im in a dream.

you can find the full article here

http://www.dreamviews.com/community/...ead.php?t=6124

its the second one "Dream reentry via "Void"/visualization method"