If you use Autostart, you MUST erase the event or turn on a self switch, if not it will keep doing it.
If you want to make a... let's say for now an intro, you will make it autostart, then put the move event, then put a wait for move's completion, put in a show text (if you want it to talk), then put in a erase event or a self switch ON, if you choose the self switch, create a new page having that self switch ON, and put nothing there (and don't put it autostart, leave it Action Button) and put nothing there.