A leak in the supply pipe.
Lots of stuf can cause it including sediment or a blocked supply line
check for leaks
Friction losses are seldom taken into account which cause drastic pressure drops
water pressure
Low water pressure or cold water main undersized.
With no air in the system anywhere, there would be nothing to hold pressure, so the slightest leak would cause the system to go to zero.
Stopped at all faucets? Didn't pay the water bill. If in cold climate, the line from the outside to probably the water heater has probably frozen.
Common signs of water pressure problems in a residential plumbing system include slow water flow from faucets, fluctuating water pressure, air sputtering from faucets, and difficulty filling up containers quickly.
Possibly a pressure reducing valve installed after piping for first faucet, which would cause situation describing.
If you mean a well tank, the water is forced in by the pump. The residual air pressure pushes the water out to the faucets.
You have to undo the aerator at the end of the faucet and clean the screen or plastic water saver out. It will be plugged with sand or sediment.
Probably not. It sounds more like a faulty water pump, water tank, or well. Most likely the water pump is directly at fault, but faulty tank pressure, bad electrical supply, or a bad well can cause the pump to do that. Especially if the surges are repetitive in nature, your pump is short-cycling. With lots of research, you might be able to narrow down the problem.