A change to Instagram rolled out to the app recently and this is how it works. When you open the picture and video sharing app, videos will autoplay with the sound off. But when you tap on the screen to turn the volume on one video on, all other videos will autoplay with the sound on for the remainder of your Instagram session. We’d say that makes common sense. And if you tap on the screen again turning the audio off on the current video, all of the subsequent videos will go silent. If you disable the sound on your Instagram videos, they will remain off when you finish your session and start up … – Source