Thanks to everyone who responded but I'd like to explain what I meant:
At 70 mph or greater there is no "feel" when the steering is on-center; the steering wheel offers no resistance to going off-center. When turning, in contrast, the steering wheel offers resistance to turning further in a particular direction.
I know this happens when you drive at high speeds, but the level of play I am feeling in my 328 is much too high.
I've driven an e36 328i loaner (just last month), an E-class Mercedes (in Germany at 130 mph for long distances), and various other cars. None had such a dead center.
At 80 mph I can move the steering wheel side to side about 1-2 inches in either direction from center.
I guess I've got to go test drive another e46--pretend like I don't already own one at another dealership.
I just hope it's my car rather than the whole e46 line.