For me it's when the page itself moves. This can be JS like some annoying ad that pushes the page content down until it is acknowledged and closed OR the worst

For me it's when the page itself moves. This can be JS like some annoying ad that pushes the page content down until it is acknowledged and closed OR the worst offender is when on mobile I click something and somewhere in between my physical click and when the click event is actually executed in the browser some additional asset or visual element loads and now I end up clicking on something entirely unintentional.