It may come down simply to how you hold your foot on the brake and steering wheel. You can deactivate the ASS or stop it from turning on by pressing firmly down on the brake as you finish stopping. You can also wiggle or adjust the steering wheel and it will turn on again. I have found that if I adjust either pedal or wheel while stopped it will turn right back on. You may subconsciously even be braking harder once stopped or even lighter and that could cause the inadvertent on or off.