erratic water pressure

My water pressure in the shower and the tub acts normal for about three minutes and then drops off from about six gallons a minute to about three gallons a minute and then returns to normal. We bought the house about four months ago and the house is four years old. I know very little about plumbing and am looking for some possible direction on this issue

Thanks
Bill

Do you have a well or are you on city water?

I am on a well system--- we live outside the city limits. I was wondering if it might be a problem with the pressure switch that is located just before the bladder( Surge tank ) ? Thanks for your feedback

Bill

With a typical well, what you are seeing is normal. The pump comes on, storing water in the tank until it reaches the upper limit. Then, shuts off. You use water from this storage system and the pressure drops until it gets to the lower limit on the switch which turns the pump back on. Depending on your usage, the pump capacity, and the storage, you might reach an equilibrium where the pump just keeps running until you turn off the shower, but usually, the pump can produce more than you are using so you go through this cycle. A cycle stop vavle or a variable speed pump can make the pressure more consistent. Check into the pump forum.