not with it
Not thinking or speaking clearly or coherently; not alert, responsive, or fully conscious. Sorry, I'm not really with it yet. Let me get a cup of coffee first. I tried getting you to leave the party last night, but you weren't with it at all.
not with it
not able to think clearly; not able to understand things. Lisa's mother is not really with it anymore. She's going senile. Tom's not with it yet. He's only just come around from the anesthetic.