Is there any halachic problem of removing one’s suit jacket on shabbat/yom tov during davening services?
Shulchan Aruch (91) and Mishnah Berurah (91:12) write that one must dress during davening as one dresses before an important person. It remains customary today to wear one’s suit jacket in front of important people, and therefore it would not be proper to take off the jacket during services. In particular, if a person does wear a jacket for Shabbat/Yom Tov, meaning that a jacket is his “important dress,” it would not be proper to take it off for the prayer service.
Rav Chaim Kanievsky (She’elas Rav, p. 194) goes to the extent of stating that it is perferably to daven without a minyan than to daven without one’s jacket!