Can one wear an automatic wrist watch (a watch that winds itself when the wrist is moved) on Shabbos? Is there a difference if the watch is put on before Shabbos fully-wound-or not? Thank you.

Though most poskim agree that winding a watch that is stopped is forbidden on Shabbat (according to the Chazon Ish, and the Chaye Adam, a Torah prohibition), if the watch is going, many permit winding, even if it is not automatic. The watch does not have to be put on before Shabbat.