Rachael, this can be caused by pipes not being sized correctly, pressure tank issues, etc; but often times when it's just one faucet it is caused by the faucet workings or seats having too much "play" in them. This allows the water to "flutter" past the valve as it's being opened and closed. (The water pressure quickly releasing as it pushes past the seal, then as pressure equalizes the seal closing back down a little, pressure builds....and so on back and forth)
To fix the problem with a faucet it may depend on the age of the faucet, but many can be fixed by getting new valve seats or valves (the inner moving part, not the entire valve body) Some are relatively easy for the average homeowner to repair; some not.
Can you tell us anything more about the faucet; single handle, double handle, old, new? Also check for additional replies to your post; there's a lot of good help around here!