It sounds as if you have a major leak. If this is happening when you aren't using water, you do have a leak. And the thermal overload may be shutting off the pump until it cools and comes on again. You could also have something sucked up against the inlet but you still have a leak because the pressure falls.
Shut off the water to the house past the pressure tank. If the pump keeps coming on, the leak is on the well side of the tank. Probalby the chack valve in or on the outlet of the pump but in the well and specifically the drop pipe or a fitting. But it could be underground between the well and the house. Look for wet spots in the yard; possibly by the casing.
If the pump doesn't run or the pressure fall, then the leak is on the house side. Toilets are prime culprits. Fill valves leaking and water running down the overflow tube or bad flapper valves leaking into th bowl. Otherwise it could be anywhere, especially if you have slab construction.
This is killing the motor and you'll just hate the next electric bill..., and you really need someone to check it out and fix it before the pump quits. I suggest a pump guy, well driller or only a plumber that is capable of pulling the pump and that knows pumps and wells.
Quality Water Associates