system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 How come snake do not form into a knot by accident?
gpt
For the same reason your tongue doesn't end up accidentally folded up underneath itself: it's a muscle that you have control over, and you have sensory input about where it is and what it's touching. So you can choose where it goes and what it does. 

It's the same for a snake. It controls its body, and can keep itself from being in a knot. It's also aware what parts of its body are overlapping other parts, as when it's coiled up, for instance. Moreover, the snake's spine has a degree of rigidity that probably prevents any sort of tight knot from forming.