I understand that you are trying to play your music in shuffle mode, but it isn't working as expected. The following info explains the shuffle feature:
Open the Now Playing screen and scroll down.
Tap to set Music to always shuffle a list of songs selected. Any album, playlist, or set of songs will play in a random order.
When shuffle is on, you'll see . To turn it off, tap the button until you see .
Play, repeat, and shuffle music
Let me know if this clears up this issue for you.