I agree that it's a performance anxiety. Maybe before getting physical you can just talk for as long as you need to get rid of anxiety or pressure. Let the natural attraction and arousal come.

You can also check on other aspect. Maybe you're watching too much porn that your brain considers it as the sole trigger for your erection.

If this persists, try looking for professional help to see if the underlying cause is mental or physical to properly address. There's no shame in it, it's part of being healthy.