Dashboard warning light for Ford Mondeo LX - engine fault?

I have a Ford Mondeo LX 1999cc 2003 Petrol saloon car. Since I bought this in August 2010 it has had a slight intermittent judder whilst accelerating through the gears. The other day it suddenly developed a severe engine judder coinciding with a yellow light on the top right of the dashboard which was constant but occasionally flashing on my last short journey. I haven't driven since... can anybody help?