I too get vertigo from time to time, seems to be associated with allergies in some way. When my allergies get band and my ears itch inside, I tend to dig at them a little with a q-tip, and either that or the itching itself (and whatever swelling might be going on inside) seems to trigger a period of time with vertigo - a week to several months.

I don't get the big hunks of wax like you, but I wonder if those might also in some way bruise the inner ear a little or press on something that results in vertigo.

Have you tried DeBrox ear drops? They're supposed to clear out wax, and maybe if you used it regularly you wouldn't get the buildup, which might help the vertigo. Maybe. Just a thought...