Car is running hot occasionally and the serpentine

Well there's only part that has to do with the cooling system and serp belt - the water pump!! Maybe it's starting to seize or has too much play. Either way, when you change the water pump, replace the thermostat and flush the system very thoroughly, those 98-99's are notorious for rust build up. Make sure to pull the heater hoses off and flush the heater core too. After all said is done, purge the coolant and make sure there is heat from the blower. If not you're going to have to replace the heater core because that gets clogged sometimes when flushing.