Mine came to me shy.
Beyond what others have mentioned regarding the feeding issue directly what I did was:
Give him lots of cover. Loose substrate, PVC pipes, plants. Assure only one side of his enclosure is non-opaque. Allow him to scoot around unseen to me.
Thaw in late evening, when I see him already poking out (he's a watcher/lurker).
Heat completely, with heat being heated via blow dryer over my body temp.
Offer via tongs in the most stable way, so the rodent can't swing/fall free/etc. Settled on hind feet.
He would take 10-15 to strike and 30 minutes to actually get it down, to start. No wonder he was skipping weeks with the breeder, since they probably couldn't sit there and wait for him to muster up the guts to strike, and his coiling response sucked back then too.
Now he strikes soon as he lines it up and can have it down in under 5 minutes.
Really focus on how your items are heated and how secure the animal feels in its home overall, IMHO.