I had the same issue back in June; it was the mode selector switch causing the problem. Another good indicator of the switch issue is if you notice your LED's on the speedo panel jumping back and forth from D, N, R, etc.

Whenever it started to act up, I could move the shifter up and down thru the gears a few times, and it would "catch", and run fine until the next time I started up. You may want to give it a try...