it's better to have an experienced person with you to manage the snake, as Udo said it's very difficult to have a good idea of the distance between the snake and the camera when you look through the lens.
you can build a light plexiglass shield screwed with a ring on the lens, so you can protect your hands behind.
on DX cameras, a 105 macro will be a 150, so you will be able to keep a safer distance...
For ground species, put them under a dark box and let them become quiet, they usually don't move for secondes after you remove the box.
be carefull