The moment I met him (at the age of 41) I had a completely alien, uncharacteristic response. I knew I wanted to be with him. I was out socially with a man I occasionally dated and he introduced me to my husband. My response was so overpowering that I said, "You don't mind if I date him, do you?" to this other person, and when he said, "Oh, I guess not," I said, "Thanks. What's his phone number?"
I found myself feeling tongue-tied and awed by my husband. It took me some time to work up the courage to ask him out, which he declined. I went on to date others for a couple months until he asked me out, but I still felt we belonged together.
Obviously, he didn't feel the same first impression, though.