Hi timoroso,
You can view all options in Settings > Safari. There doesn't appear to be an option there to stop auto-playing of videos on the internet. If you'd like, you can read more about Safari on iPad here: Customize your Safari settings on iPad - Apple Support
When viewing a video in Safari, do you see an options or settings button that you can tap? If yes, do you see an option there to auto-play videos? If you are logged in, you might even be able to find settings like this in the account options/settings. Seeing if those options are available per website/video may help resolve this issue for you.
Best wishes.