Vehicle-to-vehicle (V2V) communications have recently received growing attentions due to the fact that it enables dynamic wireless data exchange between nearby vehicles, offering the opportunity for safety improvements and information sharing. In this paper, we investigate the performance analysis of a two-way amplify-and-forward (AF) multi-relay cooperative V2V communication networks with MPSK modulation, for two cases where the relays are vehicles or they are access-points of the road. In the mobile-to-mobile communication system considered in this paper, the communication channel is modeled as double-Rayleigh fading channel. We derive the exact symbol error probability (SEP) expressions under the two-phase and three-phase scenarios followed by their upper bound expressions. Then we examine the effect of the relays' position with respect to the source terminals, on their SEP and lastly, the maximum achievable diversity order under each scenario is studied.