Today when I came to a complete stop while in D, my 2005 Honda Accord4 cylinder engine started to shake for about 2 seconds and at first I thought I might have been rear ended, only to discover that it was the engine that had caused the disturbance. So far I have not been able to duplicate this problem but I'm worried that it may occur again and leave me stranded. I accelerate slowly (usually between 1900-2200 RPMs), deccelerate slowly as well, and am a conservative driver. Do you guys have any suggestions as to what may have happened?

p.s. I'm not exactly sure but I think I saw the RPMs drop to about 400 and then go back to about 650-700 (the norm for my car) out of my peripheral vision.