Vibrato was only used very sparingly in the baroque period, from what I can find, because of the lack of chin and shoulder rests — vibrato requires free movement of the left hand, but with baroque violins, the weight of the violin was supported only by the collarbone and the left hand. I believe people would apply some for end notes, but it definitely wasn't comfortable to have the bare violin digging into the neck, so once or twice per movement. From what I can hear, historically informed performances avoid it completely.