Getting the word order right in this kind of sentence can be tricky. It feels like a question, but it's really an affirmative statement. You can see this by considering various permutations:
I want to ask you if you could help me.
I want to ask you if could tell me the time. Could you tell me what time it is? I want to ask you if could tell me what time it is.
The subject and main verb are inverted only is the sentence that's written as a question.
