An auto-responder can be a very powerful tool that allows you to automatically and quickly respond to the people who make an inquiry at your website.
Auto-responders work, but it is VERY important that all of your messages are VERY carefully written or they can backfire and come across as impersonal or disingenuous. And that is never a good start to the sales process.
If you are not a great copywriter, I would probably advise against using an auto-responder. Or, consider hiring a professional writer with experience using auto-responders.