Possible Transmission Issues

What is your question?

My car will be running fine then all of a sudden, it seems to lose some power and starts to run sluggishly. I'll look at my dashboard and though I'm actually driving...the D isn't lit up anymore. Usually after a few minutes, my car will lurch slightly, the car will suddenly run smoother, and the D will light up again. It doesn't happen all the time either. Any idea what might be happening?