What Causes Tingling And Twitching In Hands?

I have had 6 of these episodes so far. They only last 30 seconds or so. I m usually standing and doing something like housework. Loading dishwasher etc. then suddenly my arms start to fe numb. Strong tingling in both my hands up my elbows and my upper back. I can t even hold a phone to dial. I begin to feel weak all over. Do I then lay or sit in fear of fainting. Sometimes I have a strong pain in arms too. They shake and twitch. After a minute the feeling goes. Tho I m left now with a general weakened and tingling in my arms and hands. Then suddenly the attack will come on again. I ve had ct scan, ecg, blood tests. Nothing.