I have an iPhone 5 with the last version of iOS, 10.3.2. When I plug in the headphones into the jack, the music application starts automatically on the screen block, and starting to play music. I have no open application in the background when this happens. What are the reason and can be solved?
Most normal headphones don't do this but some might or might not start playing. Try pausing your music before you unplug. That should work as a temporary fix.