dcmg
If I'm reading chuckebaby's comment closely, he's referring to the specific way AUTO PUNCH works in that it needs to have the transport stopped, then R to proceed with executing his auto-punch region....not the basic functionality of simply punching in on the fly manually.
Well there's
kind of a way to do that, but you have to set it up while the transport is stopped.
1. In Preferences, check "Allow Arm Changes During Playback/Record."
2. Set the metronome for a count-in and turn on the track's R button.
3. Click the Transport record button and during the count-in, turn off the track's R button.
Now when you go over the punch point, recording will not happen unless you turn on the R button sometime before the transport arrives at the punch area.