A microelectromechanical device includes a body, a movable mass, elastically connected to the body and movable in accordance with a degree of freedom, and a driving device, coupled to the movable mass and configured to maintain the movable mass in oscillation at a steady working frequency in a normal operating mode. The microelectromechanical device moreover includes a start-up device, which is activatable in a start-up operating mode and is configured to compare a current oscillation frequency of a first signal correlated to oscillation of the movable mass with a reference frequency, and for deciding, on the basis of the comparison between the current oscillation frequency and the reference frequency, whether to supply to the movable mass a forcing signal packet so as to transfer energy to the movable mass.