volume varies up and down

"Hi

Have you checked in the Audio section of the TV Menu to see if the volume leveling setting is turned OFF?

Do not know if this setting is available to you as you didn't specify the model number of your TV.

Here is a link that explains what to do. (if you have it that is)

https://support.vizio.com/s/article/Audi..."

I had the same problem. The problem in my case was my Firestick. The firestick remote was malfunctioning and constantly turning the volume up. Took the batteries out of the remote and voila!