A disk drive unit for a removable disk (D), in particular for use in mobile devices, comprises a spindle (1) driven by an electric motor (2) and supporting the disk (D) in its operating position. It further comprises one or two loading mechanisms (4A and 4B) to load mechanical energy into a storage mechanism (5) for storing the loaded energy. A release mechanism (6) is provided to release the stored energy stepwise to the spindle in order to assist during a plurality of start-ups of the disk rotation. The two loading mechanisms (4A and 4B) are adapted to load mechanical energy provided by the user during insertion of the disk and energy released during the deceleration of the rotation of the disk, respectively. The electrical power consumption of the disk drive unit is reduced by the storage of the mechanical energy and its stepwise release.