I have a constant pressure system with the 3hp 3phase pump set at 700 feet. 2gal tank in the line. The Aquavar Solo (AS) is the monitoring unit. Pump is set to a 5psi drop. Plenty of water in the cistern. When the draw is put on the system, the AS unit gets the pump going and then the pressure drops on the gauge to almost zero. Doesn't matter whether it is a faucet, toilet, shower, etc. the water comes out at first and then barely trickles for ~15 seconds and comes on to it 60 psi. After it starts running it runs fine and keeps many outlets going. It is when it sits for any length of time that we see the above.

I also think there is only on check valve in the line from the pump set at about 300 feet up from the pump and another as it comes into the home. The pressure in the tank is at 55psi. Any suggestions here?

Just a shot in the dark here, but it actually almost sounds like what happens when a motor capacitor goes bad.

Pump only one month old.

One needs to take some voltage and amperage readings and see if the pump is receiving power immediately or if there is a delay. Therein will tell where the trouble lies.