I have a suspicion my dad went nuts recently but I don't know exactly why
What made you think that something has happened?
He was trying to cross the road and he almost got killed.
I understand feeling concern over someone's mental health. I wouldn't throw the word "nuts" around if you're not positive, though.
I'm just saying my dad was acting like a dick and I don't want friends and family like that.
And that was the only sign that made you suspicious? It is normal to be suspicious of their well being, especially if they have a history of it.