Via my friend Stephen. If you know the name of the artist or designer, please comment.
This effect is, I believe, called visual vibration, though that’s usually achieved by juxtaposing particular colours, and here I think shape/form are playing a role. This is not a gif. It’s a static image that simply appears to move.
Addendum: On the Ouno Facebook page Forest Jani pointed me to Animal Collective’s album cover, below. And this link, which yielded yet rotating snakes, and more. Click through to the link as the effect works better when the images are larger.