Hi, _Emilio_.
This is most likely a problem with a plug-in in your web browser called Adobe Flash. It's a common problem with it.
Please try viewing the videos using a different web browser. You may need to download and install them.
For example, if you are using Windows, you can try Google Chrome, Mozilla Firefox, Microsoft Internet Explorer, or Microsoft Edge if you have a new enough Windows operating system.
If you do a simple search on the web, you'll see that it is usually Adobe Flash causing this problem. Make sure you have your sound card is also enabled.
Here is a web page from Adobe with some additional suggestions.
https://helpx.adobe.com/flash-player/kb/flash-video-stops-few-seconds.html
Good luck!
Best wishes, Davin Mickelson