Have someone who knows what they are doing check the steering head bearings.
They should have just a bit of pre-load on them.
At 20k they should not need replacing or repacking w/grease, an adjustment should do.
Depending on how much stuff is in the way an adjustment should take no more than an hour.
After adjusting there should be no tight spots or notchie-ness as the front tire is swung side to side w/it off the ground (on the center-stand).
Google steering head bearings for pictars and tutorials.
Over the years I have had several Nipponese bikes develope head shakes.
Replacing the stock ball bearings w/tapered roller bearings made everybody happy.
Your BMW has tapered roller bearing fitted as stock. They should not really need adjusting at 20k imho.
So...maybe the factory did not do that good a job pre-loading them at build or the front-end has been dropped to the ground many times as it came down from frightening wheelies.
Old GSXRs have this issue.
I replaced the steering head bearing in my "new to me" "91 K75S w/67k on it. They were due for change out.
This head shake could be cause by other things, like swing arm bearings but I personally doubt it.
Post again in this thread when there has been a resolution to this VERY unsafe issue.
STOP RIDING UNTIL THIS IS RESOLVED.