There are too many to list!
In general, a silly question is one that requires, as you say, little or no thought, and to which the responder must give considerable effort to reply in sufficient words so as not to have their answer classified as "too short."
Many questions are simply yes-or-no items; others deserve a head-shaking reply of "Duh!" Some people ask questions in a way that indicates that perhaps they, themselves are unsure of what they want to know--are just asking questions for the sake of doing so.
Still others are not questions, but statements. I recently saw only a movie title. Presumably, the asker wanted a short movie review, but with only the title, it is hard to judge. Maybe they wanted to know who the screenwriter was, or the production studio.
Then, there are a few who seem to become obsessed with a given topic, and keep asking the same question over and over, with only minor wording changes.
Best questioning guidelines: Ask your question in fully formed sentences, using the "additional information" box if need be, and be sure it IS in question format, and not just making a statement.