Shimmies is much more a sympton than a illness, it is the outward sign that all isn't as it should be.
The fish generally stops in one position waving its body from side to side like a hula dancer, the movement being slow and constant.
Fish with Ichthyophthirius are liable to act in this manner; indigestion, chills, etc. are other feasible causes.
Totally changing the water frequently cures this trouble. It is believed that a micro-organism in the water of a none too clean tank can bring on this condition.
If a change of water fails, increase the temperature to a steady 80°F and feed sparingly.