The Last Hour (en Inglés) - Henry Calder

Here's the book description (blurb) for KDP:

Daniel Mercer is twenty-nine, lives in a fourth-floor flat with a water stain shaped vaguely like Tasmania, and has organised his entire life around the principle of arriving slightly late to everything. He works a job he can perform on autopilot, eats the same cheese sandwich for lunch, and watches the city move from a balcony just large enough for two feet placed carefully apart.

He is, by his own honest reckoning, fine.

Then a colleague takes the desk across from his and refuses to behave like a stranger. Then an old man dies on a Tuesday afternoon. Then Daniel finds himself at midnight, holding a piece of paper he has been meaning to write for years, wondering whether arriving late to your own life still counts as arriving.

A quiet, observant novel about overthinking, ordinary days, and the narrow window of time in which a person decides - finally - to move.