On the contrary, I believe that the dead stay dead until the eventual resurrection. Only they are not aware of the passing of time so to them, it feels instant.
And I base that belief on these scriptures:
Psalm 115:17 - “The dead do not praise the Lord, nor do any who go down into silence.”
John 3:13 - “No one has ascended into heaven except he who descended from heaven, the Son of Man.”
Matthew 27:52 - “The tombs also were opened. And many bodies of the saints who had fallen asleep were raised,”
Daniel 12:2 - “And many of those who sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt.”
There are many more which support my conclusion.
Therefore, when we die, we stay dead until the last Day. The last Day has not yet happened. While we are alive, the dead are dead in the ground, knowing nothing. Thinking and feeling nothing. Unaware of everything.
I completely understand that you will deny this because you do not want to think of your dad as being nothing, I sympathise, truly. However, the scriptures are clear.
It is amazing that many Christians will deny and ignore what the Bible actually says in favour of what they want to believe.