J.N.
My middle son thumped his head and legs. We adopted him at 18 months and he woke us up the first night with the thumping. We were quite worried that something was the matter as he had only weighed one and one half pounds at birth. We discussed it with his pediatrician who luckily was the one who had treated him since birth. He said that it was a form of stimulation. Our son continued the thumping until he was probably around 12. Check with your doctor for an opinion.