Either your window switches are bad or the motors are.
The same exact thing happened on my 92 and I just finished fixing it. There are separate ground wires between the front and rear windows. Your ground is probably bad, mine had actually broken in half in the rubber boot in between the door and the body of the car.
Because the master control on the drivers door has separate areas for all windows. Start by checking power feeds at the drivers door switch.
Probably a ground problem. Find the common ground for the lights.
I would.
The most likely problem is warped rotors. Have rotors turned or replaced. Replace front brake pads.
Usually it is the O2 sensor
old fuel filter
it would be in the relay box under the hood
That would be a timing chain for this car.
If it's a 6 cylinder , 6 , if 8 cylinder , which I think Buick does not make in that model , it would be 8 .
i have a 1996 buick century just came back from mechanic head gasket is gone and there is anti freeze in my oil i guess if you had water in your rad then you would have water in your oil.
Try checking your circuit breakers largefuses or relay switches for front power windows.
Bad fan clutch!!