I felt the urge to question my father recently.
What are you going to question him about?
I'm not entirely sure, but I feel I need to before we have an argument.
It's understandable to want to clear the air with a parent, but you do so in a manner where you both feel comfortable being open about the topic. Otherwise they may feel like they can't be transparent.
I want to ask him why he always gets drunk.
It's good to be open with your father and ask him questions to prevent any future issues. I would approach asking him the question about why he's always drunk with caution. Try to be sympathetic so he doesn't feel attacked.