I bought it 3 months ago, so I assume it's within warranty? I did a bit of reading and apparantly there's a fan inside it! Maybe it's because its been really hot past few days, but I doubt thats it as I've moved house recently and it's more ventilated than
Id not use it until you replace it. Something is wrong with it and is a possible fire risk if you leave it plugged in!!, trust me I had the same with a battery drill and charger only to find out the hard way.
If its only 3 months its under warranty ,get it swapped :)