Lack of feelings (excitement, joy or motivation)...anyone similar? ?

Sorry you are feeling that way, I can relate. It sounds like depression, it can sneak up on you and you not realize it. Talk to your doctor and let them know. Meanwhile, the cause can be so many things, everyday life. When you say you "live inside your head" that tells me you are not sharing your true feelings with anyone. When you share your feelings with trusted friends, or even online ,you can find you are not alone. If you talk to a priest, pastor, rabbi, or whomever you choose, it can help. They are trained in psychology as part of their training, free counseling! You need to know you are loved and appreciated and you touch many lives in your everyday activities. Smile more, do random acts of kindness every day. The rewards of helping others is an amazing feeling and good for the spirit. Pamper yourself no matter how little, candlelit bubble bath, manicure, massage, hair done, makeup lesson, etc. It does wonders! I could go on forever, sorry. I hope this helps a little. I will pray for you and good luck.