A mechanical self-reciprocating oscillator and mechanism and method for establishing and maintaining regular back and forth movement of a micromachined device without the aid of any electronic components are provided. The fully mechanical micromachined oscillator and mechanism are driven using only a DC power source on at least one substrate such as a semiconductor chip. The oscillator and mechanism preferably include an electrothermal actuator, that, when actuated, opens a switch to cut off supply current to the actuator. Two versions of the oscillator and mechanism are provided using distinct hysteresis mechanisms, one structural and the other thermal.