I mentioned this to one or two of you this week, and came across the video again.
The Two Cellos ( Luka Šulić and Stjepan Hauser) play a Shostakovich Prelude. They both have great vibrato, though it is very different. Watch the way their hands and fingers move. Yet it all starts back in the shoulder! That is not evident from watching them, but you can see that their whole forearms are moving. In both, notice how relaxed their hands are.
Student question: In relation to the last note, when does the vibrato stop?