When you finish listening do you back out of the app or just press the home button (leaving it in the background)? I always back out myself and don't have that issue.... If it's still occurring you can try a clean install to see if that fixes it
Please use the search feature before posting a problem/bug/idea. What's a Spotify Rock Star, and how do I become one? Using Spotify Since March 10th 2009 Twitter: @mechanimal82