(Now) where was I?

(Now) where was I?

What was I talking about? Where did I leave off? (Said after an interruption of some sort.) Tommy, Sarah! Quit fooling around back there! OK class, now where was I? So there I was, about to jump off the high dive, when—hey, I used to go to high school with that guy! Sorry, where was I? Oh yeah, so I was about to jump off the high dive.
Farlex Dictionary of Idioms.

now, where was I

I was interrupted, so please help me remember what I was talking about. (The emphasis is on was.) Now, where was I! I think I lost my place. Q: Where was I? A: You had just described the War of 1812.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • (I've) got to take off
  • be off with you
  • be off for (something)
  • be off for sth
  • be well off for (something)
  • be well off for something
  • break off
  • base off (of) (something else)
  • bounce off the walls
  • be off the wall