Is the electrical buzz that is preceding the thermostat/cooling system kicking in a sign that a component is about to die or that I'm at risk of an electical fire?

I’ve noticed over the last week or two that the cooling system (a temperature dial thermostat connected to a swamp cooler) is generating a “ramping up” buzz sound prior to the cooler kicking on. Sometimes it’s brief, but at other times it lasts a long couple of seconds. Is a system component about to die or is it a warning sign of the risk of an electrical fire or is this not something to worry about? The noise is new (as far as I remember) since we moved in a four years ago.