If you're nervously going to pick him up and taking a while to get hold of him he might be seeing you as a threat and defending himself. I had one that was a bit *****ly to get hold of so I used to pick him up carefully on a small hook about 12" long then gently get hold of him at an appropriate moment. Also make sure you don't smell like food/mice - make sure you wash your hands before you handle him.
cornsnakes, ratsnakes, bullsnakes, boas and day geckos
all good advice so far and just too add, make sure you go in to pick him up confidently, i usually go straight for the thick part of saphy's body and although she sometimes coils up if i go straight in with out hesitating she is fine