Guys, What could it mean if a guy looks 'stunned/taken aback' while talking?

[PolkaDottiers]

If a girl is talking to him, not about anything scary/out of the world, and the guy suddenly look stunned/taken aback/in a trance halfway through, what could it mean?

Is it a good or bad thing for the girl?

[Anonymous]

Bad means he has no idea what to say or how to respond and is freaking himself out

You see this a lot in anime and in shy guys. Means he has not been able to talk to girls yet and will keep doing this for a while

[PolkaDottiers]

He's very friendly and outgoing, and talks well to anyone and everyone

[Opinion Owner]

Then it's strange he froze on you? Talk to the others and your friends. Maybe he likes you but if he is friendly with all not sure why he froze

[EnjoytheDay777]

I'd need to be there to get a better idea.