Give him a week to settle in to his new enclosure then you can start short handling sessions at any time, as long as he isn't in shed or just eaten. Keep it to about 10 - 15 minutes for the first few times, then slowly work your way up from there. Sounds to me like you just got a shy snake. While bp personalities don't really change much with age, and he'll probably always be a bit nervous, you can accustom him to viewing handling as just a thing that happens rather than a bad thing to be feared.