I can't confirm that the dimensions of your cage are what is agitating your cham. There are many environmental variables that could cause this.
You'll need to provide all the details of your husbandry in order to rule out any other possibilities (lighting setup, cage temps, watering routine, feeding and supplementation regime, position of the cage/surroundings, etc.).
However, from the dimensions you listed, I can say this: your cage should always be higher than it is wide. Chameleons are arboreal creatures. They generally live in trees, and like room to climb. They also feel more secure when they are higher up (with the exception of hatchlings). So a vertically orientated cage, placed on a high table/structure would be more ideal than a wide or deep one.