In the current scenario, the growth of IoT based solutions gives rise to the rapid utilisation of WSN. With energy constraint sensor nodes in WSN, the design of energy efficient MAC protocol along with timeliness requirement to handle collision is of paramount importance. Most of the MAC protocols designed for a sensor network follows either contention or scheduled based approach. Contention based approach adapts well to topology changes, whereas it is more costly in handling collision as compared to a schedule based approach. Hence, to reduce the collision along with timeliness, an effective TDMA based slot scheduling algorithm needs to be designed. In this paper, we propose a TDMA based algorithm named DYSS that meets both the timeliness and energy efficiency in handling the collision. This algorithm finds an effective way of preparing the initial schedule by using the average two-hop neighbors count. Finally, the remaining un-allotted nodes are dynamically assigned to slots using a novel approach. The efficiency of the algorithm is evaluated in terms of the number of slots allotted and time elapsed to construct the schedule using the Castalia simulator.