nervous or uncomfortable when it comes to selling wine?

Then don’t sell.

Talk to people about something completely unrelated. Talk to them about them, ask them questions. Learn about your new friends.

The wine will sell. And if it doesn’t in one particular visit, then you provided an experience, more than mere expected hospitality.

Don’t sell wine. Be kind and welcoming, interested in your guests. You sell wine though kindness and sharing passion and love for the wine, not script recital.