1
general::
Phrase(s): set something in motion
to start something moving. • The mayor set the project in motion by digging the first shovelful of soil. • I cannot set the procedure in motion until I receive a purchase order.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Start something moving, give impetus to something, as in A press conference set the new project in motion. It is Also put as set the wheels in motion, as in Let's set the wheels in motion for the new library wing. This idiom dates from about 1800. It was preceded by put in motion, which dates from the mid-1600s.
American Heritage Idioms