When driving on HW and City, press on gas, car hard jerks while driving.

What is your question?

This situation is not everyday. But when it happens it jerks at any moment when pressing gas or stating moving car from 30-70 mph. I have sent it in at dealership twice but they can't find the issue. They reply "The computer can't find anything wrong" Now, I feel unsafe using the Jetta 2013!!! What can I do???!!