Any time you get a hot connection it comes from that particular part having a high resistance connection compared to the rest of the circuit.
So, the cause can be in your part, or in the part that you are plugged in to. Among the possibilities are: 1)the wires in your plug are not connecting well to the actual connecting spades in your plug. 2) the spades on your plug have been overheated before, and have lost their conductivity.
On the other side, in the receptacle, the grippers that grip your spades may have overheated, and so it is like a loose connection.. or the wires to the receptacle may be loose.
Both of these conditions may be present at the same time even. An electrician with a couple of meters can determine the actual problem.