Magento 2 modal: Content is showing on page load

I’m not sure what I’m doing wrong because I’m just using the official code from https://devdocs.magento.com/guides/v2.4/javascript-dev-guide/widgets/widget_modal.html

The problem is, that content of the modal is shown for a few milliseconds on every page load / page change and then gets hidden. Modal itself works, though.

This can’t be the expected behavior, so I’m wondering what I’m doing wrong. Is there any CSS I have to use to prevent modal content to be shown on page load?

Thanks