could it be the positioning of your arms and you losing circulation after a while?
palms are sensitive with lost of nerves and blood flow to it. it could be just the change in temperature or something in water to your reaction.
try to see if your palm is red by pushing on it and seeing if it turns white "blanching".
if it is not positional and your palm is a bit red you may want to see your doctor. google palmar erythema.