2000 Mercedes Benz 320e Slipping Out of Gear

My wife has been complaining about her Mercedes sometimes shifting hard, and when you slow down or come to a complete stop, it takes a few seconds to catch up to your actual acceleration, it sometimes will not shift from 1st to 2nd gear. Today I drove the car at a speed of 10 to 15/mph, the transmission jerked (like when your u-joints are going out) and when I slowed down to pull into my driveway the car would bearly move. I stopped the car and put it in park and back into drive, but it accelerated slowly (the engine's RPMs were high but it did not accelerate). I then turned the car off and back on and I seemed to reset the transmission or something. My wife says that when this happens she always has to turn it off and back on. I wanted to check with anyone before sending it to the dealership.