The rationale behind using natural movements is that our eye has already expected things to behave as the animator made them behave. The fulfillment of these expectations is the source of the psychological pleasure that translates into a high aesthetic estimate of the image we are viewing. There are a number of useful tips to avoid monotony in motion. Although a static straight line has a certain aesthetic appeal due to its geometric perfection, a monotone linear motion is much less likely to work satisfactorily - in most cases, it's simply boring. Accelerate or decelerate all instances of motion.
Constant speed adds a mechanic feeling to any movement.
Imagine that every element in your composition has a certain mass, and therefore cannot start or stop moving too abruptly. Use curvilinear motion paths instead of linear ones where possible, even if the curve is a simple circle. When moving an object along a linear path, rotating it at some degree during the shift will help to enliven it. Using rotation in combination with acceleration or deceleration will make a motion much more organic. Adding a third dimension to your motion may compensate for its too linear character.