I have custody of three grandsons, 13, 9 & 8. The nine yr old constantly clenches and releases his fist during most of his waking hours. He has been with me for almost two years now and I have asked him why he does it and he just says "I don't know". He doesn't seem to be nervous or worried, if anything he has a much better life now than he did before CPS removed he and his brother from their mother's care. When he was born he test positive for drugs (but I don't know what).