Hmm, macam circulation problem atau dia just sensitive kat temperature changes je, kalau kaki tangan selalu sejuk tapi aktif main macam biasa, mungkin just how his body is, tapi the sweating at night tu a bit unusual so worth checking dengan doctor untuk peace of mind, especially nak pastikan dia okay je. A few of my mum friends pun ada kids yang sensitive gila kat air-con, tiba-tiba mengigil then berpeluh, so maybe try reduce the AC time dekat dalam kereta and rumah, and make sure dia pakai socks plus jacket bila kena AC lama-lama. Kalau terus macam tu or ada symptoms lain muncul, better tanya doctor ye!