Why do random parts of my body have pains for no given reason?

Muscle spasms: Be aware if pain is elicited & reproducible by movements of certain muscles. This would indicate that is a muscle spasm prob. If you have chronic ongoing low back pain & were/ are an extreme sports enthusiast then is concern for pelvic girdle injury. See my chronic pain board on quora.Com to see in-depth discussion about chronic widespread pain in young males. Skateboarding is the worst.

Needs further exam: It can be many reasons. First, you need to consult your doctor to have some screening test. It can be growth pain. It can be polymyalgia, myositis, fibromyalgia, etc.