I get this warning fairly frequently. No one else who drives the minivan gets it, even my wife who drives it much more than I do.
I believe it's related to measuring steering inputs. Because I'm usually driving other people when I'm driving, I work to drive as smoothly as possible, avoiding rapid steering wheel changes, and "aiming" a long way down the road. When you get the warning, just wiggle the wheel ever so slightly to signal that you are actually driving. When my wife drives, she's often alone, doesn't worry about smooth driving, and never gets the alarm. So I take the alarm as a "Congrats on your smooth driving" award, wiggle the wheel enough to satisfy the system without passengers feeling it, and go on with my day.
(Other peoples' driving often feels less smooth than your own because you anticipate direction changes and braking since you initiate them. You have to work hard to drive so smoothly that passengers feel the ride is smooth.)