Hello, I’m having the same problem and it’s super annoying. I did all of that, close music app, sign out of iCloud, restart and I’m still experiencing the same issue. Anytime I’m working out and listening to music with the phone in my pocket and the next song plays, the screen will wake and random stuff gets pressed on the screen. I did every possible thing to try and fix it but in vein. 
I noticed the problem is with the yellow thingy in the volume level, anytime the volume is above the yellow stuff, that’s when my screen will wake on next song. If the volume level is below it the problem doesn’t happen. Is there a way to disable that??? My other iPhone doesn’t have that. Please help. I’M LOOSING IT.