The shooting pains you describe tell me this might be something other than stiff muscles, but I'm certainly no expert. Maybe some kind of disc problem? Pinched nerve? You know, just a thought, exercise caution when it comes to amateur massage, it might not be the answer, seeing as how you don't really know what the problem is.

No recent falls? No falling asleep against the arm of a couch? Repetitive strain from not sitting properly at your computer? A reaction to the bite of an exotic Australian spider?

Good luck with it.