Webamator

YouTube iframe embeds often load many unnecessary resources, which slows down your page. YEP: Optimize YouTube Embeds is a lightweight WordPress plugin that replaces YouTube iframes with a clickable preview image. 
The actual video loads only when the user clicks the play button, improving page load times and reducing initial page size.
<h3>External services</h3>
This plugin uses the external YouTube thumbnail service (https://i.ytimg.com) to display preview images of YouTube videos. 
When a page with a YouTube embed is loaded, the plugin requests the thumbnail image directly from YouTube servers. 
No personal data is sent from your site to YouTube, only the video ID (already public in the YouTube URL).
Privacy Policy: https://policies.google.com/privacy 
Terms of Service: https://www.youtube.com/t/terms

YEP: Optimize YouTube Embeds

Short Description: Load YouTube videos faster by replacing iframes with a preview image; the video plays only when clicked play.

kennethrapp

Convenient shortcodes for embedding youtube content (playlists, accounts and videos.) This plugin caches the json responses from Google’s API locally to avoid rate-limiting. Displays playlists and accounts in a responsive format, and includes title, user information, description, etc.

wordpress entuberate

Convenient shortcodes for embedding youtube content (playlists, accounts and videos)

YEP: Optimize YouTube Embeds vs wordpress entuberate