I have an AP2 Model S that I purchased new in May 2017. I do not have autopilot activated. A couple weeks ago I was driving on the highway and a tractor trailer was in the lane to my right when all of a sudden, I got a warning and the car began to steer to my left. The truck was not coming into my lane at all. Fortunately, I had a firm grip on the steering wheel and forced the car to stay in my lane but I thought it was an odd occurrence. Again, I do not have autopilot activated on my car. Any ideas what happened?