OK...
Looks like you are doing the right things (supposed you used slidestart and not pagestart ;-).
A real autostart depends on the OS.
With Windows XP this was possible, with Vista and Windows 7 you need to confirm the start (security thing).
But when the book opens and you see the navigation bar already, then the slidestart parameter should be the one to get the slide show running without further user interaction.
Did you wait long enough ;-)?