2003 Ford expedition 4.6 xtl

The check engine light is on so get it to a mechanics or a parts store and have the code read (parts stores will do this for free). The shaking is a sign of a misfiring engine, that can have a number of causes. The trouble code will give you some indication of what. Post the code here for more help.

Severe engine misfire don't listen to others saying its Ok, to drive around. Have this serviced now.

Ok thanks

A flashing check engine light means the problem is severe enough to start damaging engine components if not serviced imediately.