I'm not entirely sure what you mean by "have the DVD autostart." I assume you mean to have a particular movie play, or given you later response, for the "play all" program (movie/playlist?) to start.
Select the first play menu. In the properties panel, on the motion tab, deselect "hold forever," set the duration to 20 seconds (or whatever), then on the Basic tab, set the end action to the movie/playlist you want to play.
