Random music playing after playlist

Hello pingpsb,

That's a wonderful question. To confirm, are you listening to Apple Music via "Listen Now" in the Music app? If so, it's likely that suggestions are being played based off your listening behavior. You can learn more about listening to Music and exploring the Apple Music app via the following link.

Listen to music and more in the Apple Music app - Apple Support

Also, there is an AutoPlay feature, which you can turn off:

Let Autoplay pick what plays next

Autoplay takes the work out of choosing what to play next. Just play a song, then Autoplay finds similar songs and plays them afterward.

To see your Autoplay queue:

1. Tap the song that's playing at the bottom of your screen.

2. In the lower-right corner of your screen, tap Playing Next .

3. Scroll down to Autoplay. 

• To turn Autoplay on or off, tap the Autoplay button  in the upper-right corner of your screen. If you turn off Autoplay on one of your devices, then Autoplay is turned off on any device that's signed in with your Apple ID.

Autoplay is available only if you subscribe to Apple Music.

Add music to your queue to play next on your iPhone, iPad, iPod touch, or Android device - Apple Support

If you would like to provide feedback about Apple Music for Apple to review, you can do so via the Product Feedback website. This would allow for the appropriate individuals to receive and review any feedback you'd like to provide.

Have a great day!

This is something that happens when you have completed listening to a playlist. It just comes with the platform. You can turn it off by using the ∞ button under the queue list.