Songs disappeared from iphone!!!

make sure that you have the latest versions of iOS, macOS, and iTunes

If some of your songs are missing or the song names appear in gray text:

If songs that you bought are missing or the song names appear in gray text, they might use digital rights management (DRM). You need to authorize your computer before you can play these songs.

After you authorize, choose File > Library > Update iCloud Music Library from the menu bar at the top of your computer screen or the top of the iTunes window.

If you synced the songs that appear with gray text to your iOS device from a Mac or PC, turn on iCloud Music Library on that computer. Your library should update.

https://support.apple.com/en-us/HT204406#songs

Sign out of the iTunes Store and then sign back in.

In settings - Music - Turn off iCloud Music Library and then turn it back on.and Turn on “Show Apple Music”

Check other settings:

Settings > Music > Optimize Storage and be sure the option to Optimize Storage is disabled - if you don’t want this 

• Also check if you have enough storage space:

How to check the storage on your iPhone, iPad, and iPod touch