Couldn't it be a primitive reflex that starts a chain of locally intentional actions leading to "browsing the internet"? For example, you don't know what to write next so you alt-tab to the web browser. In itself that isn't a complicated reflex - sometimes I find myself alt-tabbing and not remembering what I was alt-tabbing for. Once you get to your web browser, you start making these locally intentional actions - i.e within the scope of a web browser's functionality - and when you finally realize what you've done it feels like one big intentional action.