Proposed is a method for operation of a first device (100) in a wireless communication system. The method may comprise the steps of: determining a sensing window; determining a selection window to be included in an active time of a sidelink (SL) discontinuous reception (DRX) configuration related to an SL DRX operation of a second device (200); selecting a resource for SL transmission in the selection window on the basis of sensing performed in the sensing window; transmitting, to the second device (200), sidelink control information (SCI) for scheduling a physical sidelink shared channel (PSSCH) through a physical sidelink control channel (PSCCH) on the basis of the resource; and transmitting SL data to the second device (200) through the PSSCH on the basis of the resource.