In this work we propose a new decentralized coding method to harness the two way relay multiple access efficiency as well as diversity benefits from a group of uncoordinated relays, via a new scheme that we call "randomized two way relay cooperation". The idea is to combine randomized cooperative coding with the two way relay scheme to attain the formation of the two-way relay channel in an ad-hoc manner, with virtually no overhead. The key idea is that through randomized cooperation the source and destination pair can be unaware of the actual set of relays that are contributing to their two way communication and still rip the benefits of the presence of a relay channel that appears has having a fixed number of antennas. Two decode-and-forward relaying strategies are considered which take up only two time slots. We analyze the performance of these techniques combined with the randomization and calculate the diversity achievable through the system.