A switch, socket or plug that feels warm, crackles or buzzes is almost always a sign of a loose connection or an overloaded circuit. A loose contact creates resistance, resistance creates heat, and that heat is a leading cause of electrical fires — so this is not something to ignore.
Common triggers are too many high-load appliances on one socket (via multi-plug boards), an undersized wire for the load, or terminals that have worked loose over time. Heavy appliances such as air-conditioners and geysers should be on their own correctly-sized circuits.
Switch off the affected point and have a licensed electrician check the connections and the circuit load. Persistent warmth often points to wiring that needs upgrading to a correctly-sized, heat-resistant HR-FR-LSH house wire.