What would cause a person to go into fits of rage about small stuff?

Short Fuse. Many possibilities, including being under extreme work or life stress; need to be perfect, using too many stimulant; steroid, or other possible medications; not sleeping at night; being in chronic pain; etc. The "extreme stress" is individual for each of us, and a huge area. Some people with post-traumatic stress disorder can respond this way also. These are just a few possibilities.