Triboelectric nanogenerator (TENG) is an emerging energy harvesting technology for potential charging solution of portable and wearable electronics. In previous studies, the designs of TENG have limitations to be used in portable applications due to the required size for contact-separation motion. In this work, we demonstrate portable self-retracting TENG (PSR-TENG) that can harvest mechanical energy through extraction and retraction process. The combination of stacking and fluttering motion during the extraction and retraction process generates multiple power peaks in a single input. Furthermore, the output of PSR-TENG is maximized by analyzing the motion of sheet dielectric and controlling the size dimensions of casing cylinder. Finally, for portable applications of PSR-TENG, we introduce pen-type TENG that have integrated PSR-TENG inside a hollow space of pen casing. This study is a potential solution for developing high power TENG, and utilizing TENG for stand-alone portable energy generators.