It was a habit of the Prophet (peace be upon him) to keep his blessed head covered with a turban or a cap. Hazrat Abdullah ibn Abbas (may Allah be pleased with him) reported that the Prophet (peace be upon him) said: "Wear imama (turban) it increases your forbearance."
(Majma Al Zawaid, Book of Dress / Chapter of Turbans 5, 199)
Moreover, Hazrat Abu Dardaa (may Allah be pleased with him) reported that the Prophet (peace be upon him) said, “Indeed, Allah and His angels send blessings upon those who wear imama (turban) on the day of Jumu'ah (Friday) during the congregational Jummah prayer.”
(Majma Al Zawaid, Book of Dress/Chapter of Imama (Turban) 5,121 Dar ul Fikr, Beirut)
Keeping the head covered was also the practice of the Sahabah and the righteous predecessors. Therefore, not only is covering the head (with a turban, cap, or a cloth) an essential part of a man’s attire but it is also “masnoon” and “mustahab”. On the contrary, keeping the head uncovered at all times is disliked and goes against Islamic etiquette.
However, there is no prohibition against uncovering the head occasionally.