YouTube recently discarded the old \"embed\" code and replaced it with iframe code.
In the new iframe code I found the way to loop+autostart videos on my website, thanks
It appears that the loop parameter requires the playlist param as well, - I'm adding the note from YouTube's documentation.
Note: This parameter has limited support in the AS3 player and in IFrame embeds, which could load either the AS3 or HTML5 player. Currently, the loop parameter only works in the AS3 player when used in conjunction with the playlist parameter. To loop a single video, set the loop parameter value to 1 and set the playlist parameter value to the same video ID already specified in the Player API URL: