Hello,
Can you review the browsers you use.
For example, if you use Edge, paste this to the address bar to launch the settings page:
edge://settings/privacy/sitePermissions/allPermissions/notifications?search=notification
Then in the "Allowed to send notifications" section, please make sure it is empty.
If you use Google Chrome, use this link:
chrome://settings/content/notifications?search=notifications
Same, also review the "Allowed to send notifications" section.
If they are already empty, can you see if you can capture a screenshot when this happens, so I can have an idea where it might come from.