As per the Notes on page 31 of the document: https://static5.arrow.com/pdfs/2018/12/12/12/23/1/848262/nvda_/manual/jetson_xavier_developer_kit_carrier_board_specification.pdf
pin 5 & 6 can be shorted for Auto-Power-On. [8-pin Header (J508) ]
Notes: - Auto-Power-On is enabled when pins 5 & 6 are tied together