i also have one of the first e36's 92' registered. the problem with your vibration is not an easy one to source if it still has all of its factory fitted components i had a vibration exactly like yours (annoying i know) also my car had the tendency to pull itself all over the road like it was trying to dance. but i can get hold of parts at trade prices so started replacing certain components first was the brakes (rear and front) new discs, pads, drums, shoes, slave cylinders etc........ it had made it a little better then came the new lower wishbones and body mounts (better still) then suspension (better still) but the one of the biggest causes of the vibration was a knackard wheel bearing !!!! (get them checked first) i also had 4 wheel aligning done wheels balanced etc........ the thing is that a 92' e36's drivetrain, bushes and mounts will all be very worn (due to age) and will need replacing! so go off my list and start renewing parts starting with bearings and wheel balancing first this should almost eliminate all problems with old bmw driveability.