I have an iPod Classic, it's three years old, and leave it plugged into the USB in my 2012 Rav4, which has the voice-activated Entune system, which is similar to the Ford Sync system, which I used to have in my old car. Every few days, I will be listening to a playlist, I turn off the car, and the next time I get in, the iPod has reset itself, or something, and it goes back to the first song starting with "A" from my entire library of songs. Which means I have to go back to the playlist and find where I was. There doesn't seem to be any pattern. I don't touch the iPod, it's in the center compartment and stays there.
I don't think it's an Entune problem because I had similar weirdness with my last car and the Sync. I use iTunes to load it and manage my playlists. I only have about 6500 songs.