Why is my engine shaking at idle?

What is your question?

I overfilled my oil when doing my oil change. Drove maybe 50 miles on the highway and when I stopped I could feel my engine shaking. I promptly returned home and changed my oil (When I drained the oil it was jet black after maybe 100 miles) and filled it to the proper level. I figured that I may have fouled a spark plug so I changed them with no luck on stopping the shaking. I've been checking to see if I am losing oil and I am not, there is no sound to accompany the shake nor have I had any smoke coming from anywhere. As soon as I accelerate past idle the shaking stops. Seems that the shaking gets worse as the car heats up, its not near as bad when I first start it. Thanks!