What Causes Frequent Body Tremors In Infants?

My grandson is about to turn 10 months old. He has exhibited a shiver/shake response since about 4-5 months of age. It happens approximately every other day and sometimes more than once a day. With my own children I never remember them doing this. There are times he seems slightly shaky but nothing continuous. He is active, alert, healthy otherwise. I am a nurse and would really like to know what might be happening. His mom has mentioned it to his doctor but he seemed not to be worried. However, we are worried. Do you think a pediatric neurologist visit is appropriate?