The cool thing about this solution is that the circles/instances maintain their distance from each other.
Here's a more advanced design, where you don't just move the positions of the circles, but where a precise chaining of circles is created.
Each circle is strung together like a chain link, giving you a nice chain.
I achieve the animation here by changing the angle between the circles with a sine curve.
Both the radius (can also be a random radius) of the circles and the amplitude and the speed of the wave are made flexible in this example.
This answer is essentially based on an answer given earlier: https://blender.stackexchange.com/a/258788/145249.
The structure here is almost identical, up to also the generation of the angles, which runs off here evenly time-controlled.