CT2004Mazda3i

sounds like a motor or pump turning on for about 12 seconds then it shuts off for like a minute or two then comes back on again(kind of like when you hear the a/c compressor cycling on and off). Ive owned the car for 5 years and it has 153k. I started noticing it a few months ago. Only happens when Im driving not at idle. Not planning on having it looked at but its drving me crazy. I just want to know what it is.