Hearing Fades In and Out - Any Ideas?

This may well even be normal but I’ve never asked an an audiology appointment. Just wondering.

Sometimes I’m listening to something/one and it’s as though someone has hit mute. Sometimes I listen to the same song at the same volume, using the same pair of headphones and it seems quieter.

It doesn’t happen all the time but it seems to happen in spates. And it usually only lasts for a few minutes.

My wife says this happens to her sometimes when she’s anxious but I can’t ascertain any pattern to it, barring the spates.

I don’t know what it could be and all my searches bring up is middle ear problems (I’ve had glue ear and it’s not the same nor does it seems to be ETD related based on my experiences) and Ménière’s (which I don’t have the other symptoms of).

Hearing loss is moderate, aetiology unknown but presumed from birth.