While I can certainly hear the question in the voice when the question mark is put there, I have to ask why on earth someone would be asking himself "I can't see the instructions"? Does he think he's gone blind? To me, it's unnatural as a question, and even worse if it isn't in dialogue. But again, if the character has adopted the raised-voice inflection and/or does ask pretty stupid questions of himself, then go with it. Just don't expect everyone to like it or even understand it.