Then the best way to phrase it would be to jump right into the question without I need your help, because saying so makes it sound as though you have more of an urgent, sensitive, personal problem than a simple question or two (they might be a bit taken aback by the phrase).
However, if you have several questions (let's say more than 2), or if you just want to sound a bit more polite, you could preface the content with a phrase like I was wondering I you might be able to answer a few questions of mine, or, I have a few questions that I was hoping you might be able to help me with.
