I’m talking about the phrase in the context where it means that the speaker is about to go into some kind of routine, most likely a dance. IN the early 1960s hit “Do You Love Me”, the singer establishes the fact that he can dance and then says “watch me work” before the break. And more recently there was a taco restaurant chain commercial where a recurrent spokesman said “watch me work” and did a dance. Variants of the phrase include things like “Have you seen him work?”, meaning “Do you know how good/bad he is”, and so on.
Was it an old theatrical or vaudeville expression?