Never be sick again, get in shape, reduce stress, a moment for yourself, get rid of back- or neck problems, out of curiosity, get to know yourself better, improve your breathing, it's something new, get out of my head, be in the now... Whatever reason you have to start with yoga, any reason is the right one, because yoga enriches your life in all ways.
Yoga makes the body and mind supple. Yoga connects your body, your mind and your soul and that is beneficial. The benefits of yoga are so numerous that it would be going too far to mention them all here, so here is a selection:
Perhaps the greatest benefit is that you are less likely to fall ill. Why is that? Yoga makes you strong and powerful, you feel fitter, it improves your posture, it makes you limber and flexible, it reshapes your body, you get longer and leaner muscles, it relaxes the joints, it speeds up the metabolism, it purifies the organs, you lose weight, it provides balance, it recovers from injuries and chronic pain.
Yoga gives mental strength and balance and that makes you happy. Yoga counteracts stress, calms the mind and gets rid of the traffic jam of thoughts. Yoga also makes you quieter, it brings you in contact with your deepest Self and you will live more consciously and with more passion. Finally, yoga gives you energy, you can concentrate better and it sharpens the mind.