My newest boy, Remi, was like that when I first brought him home. I got him from a breeder, so he was used to a smaller cage. I actually had to keep him in the travel cage for a couple of days because he would spaz out everytime I put him in his BIG cage. I made sure he had a few hiding places and covered the top of his cage with a fleece blanket. As time went on he ventured out more and more.
Now when he sees me coming he immediately runs for his tube. For whatever reason this has become a routine...he's been withe me for a few months so he KNOWS who I am (the food lady LOL). It's kind of like he's OCD and just HAS to go through the tube BEFORE he jumps on my hands LOL. Seriously, if he jumps on my hands and did not go through his tube, he will jump off, go through the tube, then jump back on my hands and look at me like I'm the crazy one...too funny.
You have to keep in mind that regardless of how long you've had your chin or chins, they will always be prey animals and their natural reaction is to run and hide. I'm sure he will come out of his shell as time passes. Good luck!