I have been losing sensation in my hands. some times i dont know how much strength i am doing or some times i can not close my hands. what could the issue? num hands

Several causes: If the symptoms come & go, that is usually a good sign (rather than constant symptoms) . If you do a lot of keyboard or factory work or other repetitive hand/wrist motion it could be carpal tunnel syndrome which is helped by use of night wrist splints & possibly ice & anti inflammatory meds. If hand grips keep weakening or numbness more constant you need Dr eval & possibly nerve testing