Why do I feel uncomfortable while sleeping on my left side?

Do you imply that you feel numbness or pain in arm/chest if you sleep on the left side? Sometimes sleeping in a particular posture can press on some nerves and cause this kind of a feeling. Also, if you have acidity or gaseous distension , you may have similar symptoms. Your physician can do a detailed examination including cardiac and neurological examination, and advice if you need any tests or not.