I honestly actually think that statement by your driving instructor is fine, if he said it in jest. It must be taken in context. If he's always been flirting with you and then made that statement, then he may soon be crossing the line. However, it's just within his nature and he wants to merely encourage you, then you really shouldn't be offended. Anyway, if you feel uncomfortable, feel free to ask him about it. I don't think he'd want to coach a student who's all wary and cannot concentrate while driving either.