Started and making good headway: by hitting one of his rare home runs, and I thought we were off and running
[1960s+ Horse racing; they're off! to signal the start of a race is found by 1833]
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with off and running
off and running
Making a good start, progressing well, as in After the first episode the new soap opera was off and running. Originating in horse racing, as the traditional announcement at the beginning of a race (“They're off and running”), this phrase began to be used more broadly in the second half of the 1900s.