Pump/Filter issue

Hi, Im new here and have new pool with 1 hp 115v waterway pump and sand filter. The pump works great - for about 45 secons, then clicks and stops. In a bit, another click and will restrat, but does same thing again. Pump is 100 feet from hardwired 20 amp dedicated circuit. I have plugged in 2 ext. cords. Check with multimeter. If I did it correwctly (doubtful) iline is a88 volts at pump and pump is drawing 9 or 90 or 900 amps. Is it likely the ext. cords causing overheating?

Also, how should the pump be grounded?

Thanks