My 5.5 yr old bro starts sweating the moment he lies down to sleep evn b4 sleeping. he sweats in the start nd then he is okay rest of the nyt, y so?

Mayo Clinic: : Night sweats are episodes of nighttime sweating that soak your nightclothes or bedding even when bedroom isn't excessively hot. They are a common problem many people experience from time to time. Although uncomfortable, night sweats typically aren't a sign of a medical problem, but they may occur as a result of certain medications and medical conditions. See comment.