To me it looks like the pump is shutting down. I also hear what sounds like a clicking in the background and if that is coming from the pump, then you definitely need to inspect the motor. I would suggest taking the pump apart and inspecting the impeller and motor. It could be that there is something caught in the impeller or buildup in there causing the motor to go into a protection mode. Depending on the age of the skimmer and pump, it could be there is an issue with the motor block. Also, as Vinny mentioned, make sure to inspect the venturi port for salt buildup inside the port where the airline connects to the motors intake. Buildup in there will restrict the airflow causing the pump to push more water than it should. While I don't think that is your issue, it's something to check while you are in there.