I advise you to consider whether you have a program that is shutting off the WiFi (or the whole phone) to save power. If the WiFi is shut off, and if the songs are coming through WiFi, then having your WiFi shut down shortly after you start listening to one song, will cause the next song's loading to cut off and not happen, stopping Pandora's playback.
Also look under Settings, under Data Management, and make sure Background Data can continue even when the screen has turned Off. Make sure it is not set to Restricted - that definitely can cause the problem you're having.
Let me know whether that helps, please.
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