What to do in full body cramps?

My dad is suffering from MND and was diagnosed in Oct 2023. He is bedridden now and since yesterday quite a few times his whole body cramps. It gets stiff and he makes painful sounds. I can understand he is in pain. To subside the pain, he is on fentanyl patch as given by the doctor. What can i do to help relieve the body cramps? His legs, arms, neck, all cramp for about 15-20 seconds and he makes painful sounds which even give me shivers. Any advice would be helpful.