Now, I got a question for you

(1)Now, I have a question for you.

(2)Now, I have got a question for you.

(3)Now, I ‘ve got a question for you.

(4)Now, I got a question for you.

If I use the sentence (4) to talk with my American friend, does this sentence sound weird or unnatural?

Now, I have a question for you.

This is unremarkable, the most standard way to say it.

Now, I have got a question for you.

The got marks this as very slightly informal, but the uncontracted have suggests that it's either emphatic or deliberate.

Now, I've got a question for you.

Slightly informal, mostly unremarkable.

Now, I got a question for you.

Informal but common in most North American dialects. Your American friend will probably not even notice that you've used it, which is a good sign.

As a Canadian, I also sometimes hear:

Now, I've a question for you.

I suspect this would also be unremarkable in Britain.