If the child has a normal set of vocabulary then not speaking a lot is not a problem comma repeated cold and cough may require some immunity boosters, please share your concerns with the pediatrician

If he DOES speak when spoken to,I don't think you have reason to worry. Speech development incorporates normal hearing and a normal brain function in addition to normal speech forming apparatus. In your case,if he can form short MEANINGFUL sentences,relax. If other milestones and brain function are fine,no problem,then. It's normal for children up-to 8 years to fall sick frequently,in fact up-to 5-6 times. If mild,avoid unnecessary medicine and just give steam inhalations for cold and cough and decongestant nasal drops for nasal block or increased cough on lying down. If not improving OR accompanied by other symptoms like wheezing or breathlessness or dullness and refusal to feed,consult your paediatrician.