Hi Reyab,
I've had a couple of these buzzing relays.
First step I would advise is to search "relay buzzing" in the EM forum and just select Topics. You'll get 6 hits straight away with good advice.
Of course I cannot help myself and will now add some advice too:
1. is it supposed to be locked on? If not, then you have something that needs fixing before you leave the machine turned on for longer than a few seconds.
2. If it is supposed to me on all the time (e.g. "lock" relay), then a couple of things: you can clean the actuator plate and the coil - they often create a sticky connection over time and can be fixed with gentle fine sandpaper getting them both back to smooth to the touch. Sometimes the mechanism is slightly out - meaning the spring maybe to tight (rare), or if its a relay that opens a "gate" that the wire connected to the physical gate is not seated just quite right.
Hope that helps.