The 1991 model E30 cars are fitted with an air bag in the center of the steering wheel. This procedure doesn’t cover how to remove that; it’s for non-airbag cars only, specifically those with the four-spoke steering wheel.
To remove the steering wheel, I make sure I have the ignition key, a flat-blade screwdriver and a 22mm socket on an extension that’s at least 6″ long.
It’s a good idea to do this with the steering wheel completely straight or to use some or other way to remember which way it’s aligned so that it goes on that same way again. Getting it misaligned doesn’t create any issues except it feels weird driving in a straight line yet the steering wheel position implies otherwise.
I use the screwdriver to pry out the center emblem, and that exposes the 22mm nut. I use the 22mm socket to remove that. Then, I turn the ignition key on, to release the lock. I pull the steering wheel towards me, expecting the washer to come loose, inside the cavity inside the center of the steering wheel assembly.
For re-installation I’m supposed to use a new nut every time, and I torque the nut to 70 foot-pounds.