Disclosed is an apparatus and method for generating energy through oscillatory motion requiring little input. Oscillatory motion is generated using a substantially circular trough containing a liquid, inflatable bags positioned below the trough and a movable weight. The trough is pivotally connected to a central point about which it oscillates. Sustained oscillatory motion is encouraged by inflating and deflating the bags in coordination with the movable weight within the trough and a biased member upon which the bags reside. The oscillatory motion may be captured and transferred to rotary motion which may be used to drive a generator.