DAD whats wrong with you?

my brother(emon) and my dad

I do not understand what happened to my father,
but since yesterday he was acting so weird
imagine,
he drive car while laughing, sometimes yelling at himself, or shows a sad face.
I know my father was not crazy and not a madman.
but his behavior is worrying us
  my brother asked
"What's wrong with dad?"
and I answered
"i do not know, I also do not understand"

whatever, it looks like there is something that offended him, and we do not know what.
today he is not acting strange, but he seems ignored us and not talk too much

dad whats wrong? :(