It could use a good cleaning. The shutter blade rack detent is stuck open, so it fires right away. Weak/broken spring, sticky helical lubricant that has migrated to the shutter, or even a broken lever could be the fault. Sometimes the levers will get burrs on them, causing malfunctions when they don't go back into place like they should. Those are the four things I can think of.
Mine is all oiled up from someone trying to "service" it. I need to get a better set of spanners so I can get the shutter out of the camera for a proper cleaning.
PF