Put on pip

Been put on 4 weeks PIP with most vague and broad metrics as if they want me to fail it which came out of no where after working long hours.. My coach hasn't been very supportive either. I have not being doing well so unsure if I should complete my 4 weeks or should I resign. Talent/HR havn't been very clear either what happens after 4 weeks. Any insight would be helpful as market is not very good right now.