Agree with XiaoDeng,it sounds impolite.you can say 我想问下/我想问的是

谢谢！

Yes, but it would be less polite, maybe even rude. But wearing a smile and bright voice can eliminate that sense. Or you could change by saying我想说/问的是 (what I meant to say/ask is ...) more polite, 你好，我向想问的是… 不好意思，我想问的是…

When you are correcting sb that you are asking this not that,then you can say 我是问...（不是....），but if you just wanna I’m asking... you can say 我在问....