I don't do a lot of animation myself. 

But if I should do it, I would do something as I have done with my "Salmon" as a fish kind of moves similar to a snake. Obviously, the big difference is the huge amount of bones in the snake compared to a fish, which makes it difficult to animate.

What I did with my fish is to create morphs for controlling the movement easily.

So in this case, these 3 morphs control several bones at once, so you don't have to animate each individual bone.

Here you can see how that would work

Swimming fish

Depending on the snake model you are using, it might already have such morphs, otherwise, I would suggest making those first and then using those to animate it. You can then link it to a path afterwards and if you spend a bit more time on it than I did with my fish animation, you can probably make it crawl. Also depending on the scene you are making, using some clever camera cuts would probably make it a lot easier as well.