HpOoRwSeEr

when im driving around anywhere, every now and then i loud humming noise comes from the engine bay when im not on the gas it will hum for 5-6 sec if i dont do anything. but if i just lightly put my foot on the gas it stops. then 5 or 10 minutes later it randomly does it again, i give it a little gas, and it stops. this happens through all the gears and at any speed.