It may be dehydration from lack of water/hydration /alcoholism. We we wake up we drink coffee or water and/or other fluids and with movement they hydrate our muscles.
Has your husband got arthritis? I have an arthritic back and I get bad cramp in both my calves, which eases as I move. I just accept it as part of having an arthritic back. Nerves can get pressed upon. Just keep moving. I have exercises I do for back pain. I don't worry about the cramps.
Obviously if your husband is worried, he must see a doctor.