Probably your alternator.
replace your head light switch
I have an 2005 and the headlights on it will dim, and then brighten back to normal. I bought it brand new, and it has done it since I bought it. I actually took it back to the dealership, and asked them about it, and they said that Chevy knew that it would do that, but that the car would keep running, and that there was nothing that they could do about it. Hope this helps.
it is caused by the alternator voltage regulator switching on and off to charge the battery, this problem is encountered on many makes of car, you may not of noticed it before prior to exchanging the battery.
Alternator is failing.
a flat battery
On my 89 Probe it overcharged because I needed a new alternator. Sometimes a bad computer causes "spikes" in the voltage. In this case, turn the headlights on at night, if they flicker like high beams, then the computer is NG. -CE
The primary causes for the lights to flicker inside on a 2002 Chrysler Sebring LXI is a loose bulb or wire. This can occur when the vehicle has experienced rough road conditions and excessive vibration.
there could be a few things to look at first , is the check engine light on? if so then you want to get a shop or auto zone to run a computer diag on it you will probably find either a mass airflow meter or the idle air control is bad you can mail me @ tajohn4u@aol.com for further info
What_is_a_loud_humming_from_car_light_motor_after_in_lowers_down_and_closes_on_your_1997_firebird
I think it is a dying battery
A monitor may flicker due to a poor cable connection. Other causes include electrical noises and over-sized speakers near the monitor.
What causes a 1998 Pontiac transport to run hot and engine shuts off