What do you mean auto? You have to invoke the command for it to sync. Once you run a full sync via cable, you will see an option for wifi sync in iTunes under iPhone. Once this is checked, even if you disconnect your iPhone from the cable, the iPhone should still show up in the left pane. Here, you can click on the iPhone and then click on Sync and it will begin to sync. Well, it will first look for your iPhone and then sync.