Again...intermitten noise is very indicative of CV joints early failure. I have spent several years as a rotating equipment specialist working for BP in chemical plants. I have analyzed and witnessed tear downs of hundreds of ball and tapered roller bearings. I've never ever seen a bad bearing in failure mode quiet down without intervention (a squirt of grease or tightening of float)... they always gets progressively worse. They also are generally independent of the throttle. About the only thing that will change the noise is reversal of direction, or change load (cornering or adding weight to the vehicle). A wheel bearing's purpose is to provide radial and axial support to rolling shafts.

CV joints on the other hand are very throttle sensitive, because they transmit the power to the rear wheels. They are very big (relative to bearings) and have less constraint than bearings (inches of end play as opposed to a few thousandths), which allows them to find different running areas. In certain positions they can make noise and in others they run fine. Most noisey joints are being starved for lubrication, and moving them laterally tends to temporarily redistribute lubricant to needed areas. At very advanced stages of failing the noise will become more consistent. That is why I suggested getting some lubricant into them could solve your porblem. I also suspect that even though you don't see failure of the boots, you may very well have lost a substantial portion of the lubricant - possibly through a loose clamp or even a small crack. The oil that is used is much like gear oil, which you may be able re-inject somehow??? (a big scringe??). I suggested grease as replacement, because it is easier to contain than a liquid.

Good luck.

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1976 240D
1987 560SL
2007 E320 Bluetec
1998 C280 (now son’s car)
1982 240D Manual - Sold