While the instantaneous power of triboelectric nanogenerators (TENGs) has significantly increased, the average power remains unsatisfactory. Achieving a continuous and stable output remains a significant challenge. Herein, a self-excited vibration TENG inspired by woodpeckers is proposed. This structure converts gravitational potential energy into the continuous vibration of a cantilever beam. A dynamic simulation model of the system is established, and the influence of different structural parameters on the motion characteristics and electrical performance is discussed. Meanwhile, the experimental results indicate that the accelerated motion (approximate free-fall motion) is transformed into approximately uniform velocity motion. For a 3 cm² TENG, the instantaneous power density reaches 2.03 W m⁻², and the average power is 127% higher than that of the conventional cantilever beam mode. The proposed self-excited vibration mechanism is a promising approach for enhancing the average power and operational duration of TENGs. It shows great potential in fluid energy harvesting.