Pain on my left arm and shoulder from typing as of now. what could this be?

Few things: Straining muscles involved with typing by keeping them in wrong position instead of relaxed hands and wrist cocked slightly at wrist, and not 29 inches off the ground sitting on a proper chair. Or it may not be the typing. Doofus u have any heart disease? Always keep open mind about what is going on. A good diagnostician is constantly doing this as she/he heard the story.