Mark, I had a similar problem a few years back. I would be driving on the highway at speed and all of a sudden my car would just jerk maybe once or twice. It was strong enough that I could spill my coffee if I wasn't careful. Dealership never could find any kind of problem later that year I did change my fuel filter and did some other stuff and, "touch wood" that problem has never come back since. I have no idea if those things helped.
