Is it better take your shirt off for massage?

usually yes, unless it is chair massage or in a public setting. It is easier for the Therapist to use different techniques on bare skin using oil or lotion.

However if you are very uncomfortable being exposed discuss it with your Therapist, (we understand) they may suggest keeping clothed until you are comfortable, also keep in mind that in the U.S. laws require that only the area being massaged be exposed the rest of the body must be covered with a sheet or blanket.