Why do I get shooting pains in my legs?

So I'm a 21M and for some years now I've been getting pains all of a sudden in my legs. I probably get several per day, and the pain is unpredictable, i.e. I may be sitting or I may be moving or I may be sleeping. I've heard that it's either because of salt or potassium but I don't know how it works. ELI5.