More often that not, I see sentences like the following:
I wonder what time Mike will be arriving?
Guess who I met at the basketball game?
“Wonder” and “Guess” sentences are almost always punctuated (incorrectly) as if they were questions. In fact, they are declarative sentences.
In the first sentence, you are not sure what time Mike will arrive. You have a question in your mind: Will he be here at three o’clock? Four o’clock? You just don’t know. But your sentence is not a question. You are merely stating the fact that you’re unsure when to expect Mike.
In the second sentence, you are asking someone to guess whom you met at the game. That person doesn’t know. But you know and, in fact, you are ordering the other person to do something: to guess who the mystery person is. The sentence is a command, not a question.
I suggest that when you write a “wonder” or “guess” sentence, check specifically to make sure you’ve used the correct end punctuation.