All of mine are head shy when I first pick them up. After I handle them a while, I can touch their heads, but they do best when I touch their heads from the back.

I think that head shy is a survival technique. A snake's head is it's most vulnerable spot. None of my snakes have really liked having their heads touched from the front. But I do have a piebald who will sit motionless while I stroke the soft parts of her head on the sides of the midline when I do it from the back. I think that she actually likes the sensation. I also think that coming at them from the front is something that they perceive as a threat.