'Static' type noise under light acceleration

[00_Bora]

Hi all - I'm trying to diagnose a sound that's recently developed on my 35i around 90k miles that I cannot track down. Sometimes at idle (random times and temperatures) and then under very light load (like reversing or starting to move under 15-20mph), my engine bay has a noise that I can best describe as a 'static' noise like an old TV channel that was not working with a hint of metal involved.. Its rather loud and disappears after some speed, but I cannot track it down in my head.

Thought maybe after an oil change, it may disappear but no luck. I dont believe its the belts since the noise does not match to what I know as an aged/dry belt sounds like.

Has anyone else ever experienced this? I'll try to capture a video of it, but its hard to capture from inside the cabin when moving.

[RED_Y_]

Video would be helpful, may be some bearing on the pulley/tensioner/roller is dying?