Why my hand till my arms always? Cramping

Many caysesv. There are many possible causes with possible hypocalcemia and nerve compression with subsequent denervarion and fasciculation being more common reasons. See your primary care physician fitst.
Overuse. It may be an overuse phenomenon. Are you more active ? More active at work? It could also be a nerve compression like carpal tunnel syndrome or maybe even an issue in your neck.
Carpal tunnel? Cramping of the hands has several causes. Probably the most common is carpal tunnel syndrome, due to pressure on the nerve at the wrist. There are rare muscular diseases that can cause cramping, overbreathing or low calcium can cause cramping.