Q: Pressing on gas pedal, car loses power - 2010 BMW 335d

While exiting the interstate and trying to pass a slower-moving vehicle which was in front of me, I passed it and then accelerated. Surprisingly when I pressed on the gas pedal my car lost complete power for 5-8 seconds. The car I had just passed nearly rear-ended me because naturally, they had not expected me to pass and then reduce speed. I carefully got to the dealer who claimed that he had never heard of such a thing. They could not duplicate the problem and they told me to start driving in the sport mode. Since then (about 1 ½ years), the same problem has happened twice and each time the dealership could not replicate the problem, so there is no solution for me. I need your advice as to what will fix this problem.