The presence of multiple WBANs in any location leads to co-existence issues as multiple users occupy the same channel at the same time. In a real scenario due to mobility the co-existence issues arise intermittently depending on the closeness of the mobile WBAN and other static/mobile WBANs. Since WBAN’s are used for monitoring the vital parameters of the human body, the performance of the system consisting of multiple WBANs gets affected whenever co-existence issues arise. Existing work deals with interference issues that arise in Intra WBAN communication. Very limited work is present in literature dealing with coexistence issues that arise from Inter WBAN interference due to varying mobility. In this work we evaluate the performance of the system consisting of static/mobile WBANs subject to interference under varying mobility of other WBANs passing by, thereby creating Body to Body Networks for random, intermittent time durations depending on the speed of the mobile WBANs. We consider two cases, a park area with surrounding paths and an old age home located on a roadside with passersby. We propose an optimization technique using WOA to determine closeness between the WBANs and evaluate the performance of the system. We also consider the case of the impact of passer-by WBAN mobility on static WBANs (elderly occupants of an old age home) and develop a hybrid WOABAT approach to determine the optimal positions for the static WBANs such that the entire system performance is optimized.