iPhone autoplay error with wireless headphones

I have the issue that my iPhone / iPad automatically starts playing random music when I put my Apple Airpods or Powerbeats headphones in my ear. This is really annoying!

I connected the headphones to iPhone, iPad and Apple watch. I followed all community advice and unticked boxes in the music library, also handoff etc. is switched off. Still music keeps playing when I put the headphones on. I could only solve the issue with the iPad by deleting the iPad's music library. Now the same happens with my iPhone. Also disconnecting the headphones from my iPhone is not a solution, as I need them listed in the iPhone in order to operate the headphones on my apple watch. There is no button anywhere in the settings to stop this. Do I really need one device to operate the Apple watch and another one for my music library to stop this random music playing? Please help!