Should a question masquerading as a declaration—like, "I wonder if you have any suggestions?"—end with a question mark or a period?
The correct answer, originally, is that no question mark should be used and that instead, a full stop should. Since the main idea is that "I wonder", which is just a normal 'stating' clause and not a questioning one, and also since you are technically not expecting an answer, a question mark should be absolutely unnecessary. However, the contemporary usage of this phrase - "I wonder" - along with other phrases such as "because... (I can)?" or "surely, none of you can dare to disagree?", has been that of a question, and so placing a question mark at the end would still be acceptable. For the same reason, by the way, people do not usually place a comma after "surely" in sentences such as the one given in the example above, considering it to be the questioning clause, i.e. thinking it to be equivalent in meaning "isn't it evident that".