Tics can arise from several sources. Sometimes they are manifestations of neurological disorders, sometimes they can be related to stress, sometimes they can be prompted by medications, etc. In children, it is not uncommon to witness transient tics, tics that appear and then disappear without treatment. Multiple motor tics in the presence of at leat one vocal tic can be indicative of Tourette Disorder, and this may be what you are witnessing in your son. It would be prudent to obtain an evaluation by a pediatric neurologist.
I wish you the best with your child.