I have the same issue and I'm getting annoyed with it...
Uneven tyre wear diagnosed a year ago. I couldn't see it until it was pointed out to me, but it was quite obvious / pronounced. 4 wheel alignment and new tyres appeared to resolve it.
12 months later, it's back with a vengeance. Can't see any uneven wear, but then I couldn't last time. Unclear if the 4 wheel alignment wasn't done correctly and didn't resolve the original issue, or if something else is at work.
Swapped wheels front to back with no change, but I can't be sure the rears haven't already been on the front and already picked up the uneven wear too.
Had the wheel balance re-done (cheapest option first -no improvement). 4 wheel alignment done again (different place), with no improvement. Plan to get two more tyres on the basis that correct alignment on already worn tyres isn't going to show anything.
For me the car will sit at steady at a steady 45 all day long. Accelerate from 30mph through 45mph and there is a wobble. The harder I push it the worse it is. By 50 it's passed, and nice and smooth again. There is a barely noticeable wobble at about 22mph too, which makes me think it's a resonant, but I can't figure how it only shows under load and not when driven steadily. I guess the next point would be at 90mph, but I don't tend to go there.
It shows up at the same road / wheel speed regardless of engine speed (in gears 3,4,5,6). 45mph in first or second doesn't seem like a good idea. This makes me think it's less likely to be engine / clutch / flywheel but I could be wrong.
It seems much less pronounced on a cold morning. Not sure if that's before the tyres warm up and grip better, the oil is thicker in the engine / gearbox / dampers, or is just coincidence.
It's not felt the steering wheel as such, it's the whole front of the car. I can't reproduce it when braking from 60 through the 45mph zone, it only seems to be on acceleration.
I wondered if knackered dampers might be involved? The nose doesn't rise noticeably but I wonder if it's going light at the front and scrabbling for grip.
Possibly drive shafts or diff? But why only at one speed? Might be an expensive thing to prove.
My discs are worn and will be replaced before summer is out, but I don't think they're involved.
Any ideas would be appreciated...