That can happen when the fan is failing.
Check the resistance on the blower motor.
Common causes, blower motor resistor, blower motor, wiring or controls
the blower fan resistor has gone bad.
If you are referring to the blower motor speed control, and you only have one speed, then the blower motor resistor pack is defective and must be replaced.
The blower motor is failing and drawing too many amps.
Inspect the backside of the blower speed switch. Look for an overheated, melted plastic connector. Loose connections causes resistance, resistance causes heat, heat causes melt down. Look for melted connections at the blower motor and resistor also.
blower motor resistor is burned out
The blower motor speed resistor is probably burned out.
Defective Blower Motor Resistor Pack.
Check the fuses.If not the fuse, test the resistor down by the blower motor.
usually what causes that is the blower motor resistor. Get a volt meter and test it according to it's values, 90 percent of the time it's the RESISTOR.
Defective Blower Motor Resistor Pack.