The phrase "silly question" refers to a question that is considered unimportant, obvious, or foolish. It implies that the person asking the question should already know the answer or that the question itself is not worth asking. Full definition
These may seem like silly questions, but I am not a tax expert. (remonline.com)
I could ask silly questions about christians, what good would it do me? (religion.blogs.cnn.com)
Replace the word «salespeople» with «teachers,» however, and we move from the realm of silly questions to the arena of intense policy debate. (educationnext.org)