You can let your video start playing automatically when a user visits the page, by adding autoplay=1 to the YouTube URL. However, automatically starting a video is annoying for your visitors!
Note: Chromium browsers do not allow autoplay in most cases. However, muted autoplay is always allowed.
Add mute=1 after autoplay=1 to let your video start playing automatically (but muted).
Live Demo & Try it yourself!