Movement is instinctive. We're designed to move and express ourselves through movement. Toddlers will stamp their feet if they're unhappy or reach a little hand out and animate their fingers to show they want the snack within grabbing distance. Growing up sucks a bit, because we learn to control the body.
Humans, like other animals learn to move through observation and imitation. Just like developmental movement (the process you took to get from crawling to standing), learning specialised movements like yoga can also become second nature.
Practice intelligent yoga that honours the physical body in that moment. When taught well; yoga does not discriminate with regard to size, age, ability, religion, health or human performance.