iPhone 6s battery suddenly draining quickly

Hi all, yesterday my iPhone 6s suddenly shut off after being at 97% battery. When I tried to turn it back on that image indicating that I need to charge came up:

I waited a few minutes and then it let me turn it back on, but the battery was only at 10%. I did a hard restart, and then the battery was at 90%, but after that it started draining really quickly and also started to take forever to charge.

It's fully updated in terms of its software - it's on 13.5.1.

One anomaly that I've noticed is that the Music app has taken up 39% of the battery life over the past 24 hours, even though I literally never open / use it.

Any insights as to what's going on? Any recommendations?

If it helps, when it shut down I was just starting to use the Runkeeper and Spotify apps.