Looks like that pump has a built high pressure shut off switch that when back pressure builds up to a pre-set level, it stops/shuts off the pump. (i.e., if you use this type of pump as a wash down pump and you have for example a shut off type spray nozzle attached and it's closed, the pump auto shuts off but, then turns the pump back on as water is used)
This type of pump can do what yours is doing if there is a small leak somewhere down stream and pressure is slowly leaking off, the switch turns the pump on for just a second as pressure decreases and then rapidly shuts back off due to the pressure going back up.
