89 Accord seems to shift and lunge while stopped

I have an 89 Accord. It is an automatic. Often when I come to a stop, I will be sitting there with my foot on the brake, and the car will drop a bit in rpm's as if it shifts, then it feels like it lunges forward. I don't think it ever really moves more than a couple of inches (because I have my foot on the brake while stopped). Then it will go back to idling normally. I tried to pay close attention last time and I noticed that the check engine light came on right when it did it last.

This may be unrelated, but since we got the car five years ago, it has always had a little bit strange behavior at about 60 mph. It shifts back and forth between gears. I am not sure if these two are related or not, but I just thought I would throw it in fyi.

One other bit of info. I am not positive, but I think the behavior started right after I took the car in to Jiffy Lube. Probably totally unrelated, but I just thought I would throw that in.

Any ideas?