Ever since the upgrade to iOS 8, Spotify has become really flakey, and I have the latest Spotify installed on my iPhone 5s with iOS 8.0.2.  As I'm driving, the music will stop, and no amount of mashing the play/pause button will get it to resume playing.  Other apps that interact with the network function correctly.  Once I've restarted Spotify (by terminating it and then restarting it), and hit play, it immediately says that I don't have the song synced for offline mode, despite being online.  Then I click through that dialog, tell it to play again, and it starts playing the music.

I suspect that my phone might be latching onto passing wireless networks while I'm driving, and this might be confusing Spotify to the point where it can't recover once the phone returns to LTE.  I saw this happen when a bus drove by me in the carpool lane, while I was stuck in traffic, and that bus had a wireless network for which my phone is authorized.

I have a premium account.