In absence if trauma. You must look for one cause which could be from spinal cord compression or metabolic or vascular. I would suggest you see your primary care physician for a neurovascular review in addition to general history and physical with diagnostic testing or imaging where indicated.
Both wrists? Sounds inflammatory to me. Wrist invovlement is quite common in early psoriatic arthritis and rheumatoid arthritis. Need a diagnosis. See your doctor!