Third Generation Partnership Project (3GPP) has standardized the Sensing-Based Semi-Persistent Scheduling (SB-SPS) as the radio resource allocation algorithm for 5G New Radio vehicle-to-everything (NR V2X) sidelink communication Mode 2. The algorithm leverages on resource reservation information of neighbor vehicles to reduce the chances of packet collisions. Like in LTE V2X, the SB-SPS scheme in NR V2X also assumes chained reservation that reflects the periodic nature of the traffic. However, such scheme does not work properly when the next packet instant is not fixed. Because NR V2X introduced aperiodic traffic, the limitation can be a performance-limiting factor in NR V2X. Therefore, we propose an enhancement to the SB-SPS algorithm to reflect the stochastic nature of the aperiodic traffic on the resource reservation mechanism. We demonstrate the effectiveness of the proposed enhancement through analysis and simulation, and discuss its cost aspect as well.