Keeps deleting downloaded songs

[Combmatt]

I'm running iOS 10.2.1 and this has been happening over the past few months sporadically. Interesting thing, though, it doesn't delete the songs that are in playlists that I've downloaded. This is really annoying though because 2/3 of my downloaded music isn't in playlists and I feel like at least twice a month I'm downloading 2,000 songs all over again. Please help!!