Why is my phone's volume changing without my interaction?

[Android Central Question]

So, my phone's volume, without me manually changing it, has been shifting between loud and soft. This is not a hardware phenomenon because I've seen the same thing happen without headphones, with headphones and connected to my car stereo. It's not changing to various levels, rather, it changes distinctly between two volumes. Since this has been happening, I have been keeping the volume at the full setting because, if it dips as it has been, it becomes extremely hard to here.
Furthermore, this happens in more than one application. This same pattern happens in YouTube, Facebook videos, Google Play Music, and Spotify. Even more rarely, it, without me having any contact with the phone will completely pause the video or source of the audio. If it is Google Play Music, it can pause. If it is YouTube, it can pause.

My phone is a Galaxy S5, and I have had it for years. I am able yet unable to replace it through the carrier because for college I have lived away from the carrier which would directly deal with it. The main point is to ask if I can do anything to stop this before I am able to replace it with the carrier.

 

[B. Diddy]

Welcome to Android Central! Does it sound like that through both the main speaker and also through headphones? Does it persist in Safe Mode? https://support.t-mobile.com/docs/DOC-28456

 

[ADenys]

B Diddy, This seems to have stopped it. P.S. is there a way, to comment back to the answer without submitting a new answer?

 

[B. Diddy]

Glad it seems to have resolved! But let us know if the problem comes back.

Creating a new reply in the thread is the best way to continue the discussion, rather than modifying your original post. You wouldn't be able to modify it in this case, anyway, since you made the original post as an unregistered guest.