I find that that the Ipod (or iphone - doesn't matter) will fail to resume after shutting down the bike - at least 80% of the time. As oe542bob mentioned, I have accepted and gotten used to this quirk. The only successful solution for me - also mentioned by others - is to cycle through and reselect the playlist, select shuffle, and then select the next track. An annoying side effect is that if you don't select the next track, you have to listen to the first song in the playlist every time (in alphabetic order), so I am now sick of "Achilles Last Stand" by Led Zep. I know, I can delete it, just too lazy.
Does anyone else find it counter-intuitive to have to push the selector switch "up" to go to the next track? It seems more natural to push it down, and less awkward. Nit picking.