Are shaking chills unusual with mild cold and cough illness?

Yes. Shaking chills and fever can be a sign of a bacterial infection. Often time pneumonia will start first with a viral illness such as a cold but if bacteria grows in the lungsand cause pneumonia, shaking chills, fever, worsening symptoms of cough, discolored phlegm begins. At that point a chest xray/medical evaluation and most likely appropriate antibiotic treatment is needed.