My music volume goes in and out as if I'm gettmultiple notifications but nothing is there

[Musicaly lucid]

I have a galaxy s5 and I am having this problem that when I listen to music on soundcloud the volume will fluctuate like when I get notifications but there are no notifications and it still happens when I pause and unpause the music and end up having to restart the phone. Please give me a solution!

 

[B. Diddy]

Welcome to Android Central! Does this happen regardless of listening on the main speaker vs using wired or Bluetooth headphones? Is it only with Soundcloud, or does it happen with other music apps or services?