What Causes Sweaty Hands, Feet And Armpits In A Baby?

My baby is 3 and half months old and has always had sweaty hands, feet and armpits. He gets hot easily and sometimes gets cold clammy sweats. His chest and tummy often feels very cool to touch. I m so worried about this. Could you advise me on what could be causing this? I stupidly read the internet and have scared myself silly on the things ive read such as heart problems and linked to SIDS. Thank you