Just adding my two cents worth. I am also a premium Spotify member and am seriously considering canceling due to the ridiculously slow performance of the app. It often will endlessly spin and not load my library or playlist.
This is ridiculous- Spotify is almost un-usable on desktop (PC)... it is so ridiculously slow. And like others, I tried several fixes, one of which worked for about a day but it's back to being slow. Can't believe I pay for this **bleep**.
Yes, unfortunately the solution I posted was only for windows/mac. In terms of a tablet, it could either be the app or your tablet - ensure you have the latest up-to-date version of the app, ensure you don't have loads of background apps running and close apps you're not using.
If it's down to the app (which it could be), only thing I can think to suggest is to go into settings (go to Your Library, then to the cog symbol, should be top right) and clear cache and saved data. This will clear your settings but won't affect your account (playlists, followed songs/artists etc.)
There isn't really many settings in terms of the performance of the app, asides from the stream quality settings.
If all else fails, try asking @Spotifycares on twitter regarding the tablet app.