I had the same issue when starting back up recently. I started concentrating on competent warm up techniques before digging in. I do about 5-10 minutes or so of scales starting slow then speeding up with each run. While I still get cramping in the wrist or back of hand I have noted it is taking longer and longer for the pain to start. Basically you are developing unused muscles with repetitive practice. It won't happen over night. It is really no different than going to the gym. You exercise till you "feel the burn" I just wish I could find more exercises to feel the burn in my picking hand. My fretting hand is way faster than the pick.