Q: volume is lowering itself  sporatically every 30 seconds or so after I raise it- any thoughts on how to fix it?

all of a sudden during my run tonight the volume is lowering itself.  I checked to see if maybe the - button was stuck down - but it appears to be ok.  It will keep the volume setting where I raise it for about 30 seconds and then lower back down to quiet.

Any thoughts?  I tried to reboot it - but that didn't work either...