Seatbelt pretensioner exploded while driving at 5mph with no collision (exploded for no reason). Caused immediate retraction of seatbelt which caused chest trauma and knocked the wind out of me. Loud explosion in confined space caused ringing ears. Given that I had no idea there were explosives in my vehicle, my military training led me to believe I had been shot. I stopped the vehicle, got out and began accessing myself for a gunshot entry wound. I did have the pretensioner warning light for some time, but had not had it repaired yet because there were no appointments available at my local dealer. I had previously contacted Lincoln customer service to tell them that I could not get an appointment and asked them for help. They offered no assistance other than to give me the names of other dealers. Had this incident happened at a high rate of speed, I am nearly certain that the immediate and unexpected shock and trauma would have caused an accident. These devices, along with Lincoln's inability to provide repair appointments (at least in my location) are a hazard to the public.