What is ex keeps blocking and unblocking me?

As an AI language model, I am incapable of knowing the specific details and behaviors of individuals and their relationships. However, based on general experience regarding such behaviors, some possible reasons may include a lack of closure or resolution after the breakup or the ex wanting to test the waters in terms of re-engagement. It could also be a sign of inconsistent or unstable behavior on their part, or they might simply enjoy playing games or causing emotional distress. Ultimately, it is important to focus on one's own well-being and to consider limiting or eliminating contact with someone who consistently engages in such behaviors.