The other day I was stopped at a red light and driving with the transmission in "D" position. The light turned green and when I stepped on the gas peddle the car wouldn't move, the peddle felt limp and in didn't even rev. At this point, I tried to manually downshift to 1st but it wouldn't come out of drive. I put it in park, turned the car off, restarted and it ran fine. Since then I have been manually shifting but yesterday when I shifted to 3rd, it just stuck there until I pulled over and restarted the car and it was fine again. Any ideas?