You have to chose in the options for the videoplayer autoplay or no autoplay if you do not want to play them.
Please do not forget that the fluently replay of videos depend on the PC you use, your internet connection and your provider - and of course on the size and format of your videos....
The video has to be loaded....if you have a slow (or busy) internet connection or - what also may happen - the server of Magix is a bit busy, you'll have to show patience ;).
It'd help here to have a link to your page, I'd like to see the video. Maybe it really is very long / big...?