- Force quit the Music app.
- Restart / Restore your iPhone.
- Turn off Automatic Downloads (Settings -> Music -> Automatic Downloads).
- Disable background app refresh (Settings -> General -> Background App Refresh -> Disable Music).
- Turn off Mobile Data (Settings -> Music -> Mobile Data).
- Cancel all downloads in the Music Library.
None of them is surefire correction, so you may have to try some before something works (if it’s at all). If you delete and reinstall the Apple Music app and you are still on the frame of your iPhone’s battery, even after trying these additional changes, the only option is to delete it at the moment. Here we hope not to bathe your playlists too, or don’t worry about listening to your home page or web browser, at least.