200 fosue se hard idling

Our 2000 Focus Se idles "hard" when first started for a bit until warmed up.It doesn't really "miss", but the whole car vibrates and shakes somewhat.A code scanner brought up nothing. Once it's warmed up, it's not great, but a lot better.
Stumped.

It's time for a compression test to see if cylinders are about equal (within 10%) with each other. I would also use some Chevron Techron to clean the fuel injectors. It's available at Auto Zone and other auto supply stores. Does the engine idle at a higher speed until it is warmed up? When were the spark plugs replaced last? When you do a compression test, chack the condition of the spark plugs.

Spark plugs were changed about 6 mos ago.
It seems to idle higher until warmed up; idle drops a little, and it's not as "hard" or "rough" as when first started.

Did you install Motorcraft plugs and are you sure they are gapped correctly? Did it run like this before changing the plugs? How old are the plug wires? Try the Techron in two tankfuls and see what happens. The rest of my advice still stands.