What causes noise and vibration in the brakes, that goes away after warmed up? on 2000 Toyota Sienna

When the van sits over night, the first time you apply the brakes there is a noise and a cycling vibration in the brake system. What could be the problem?

Asked by for the 2000 Toyota Sienna
brake possible not releasing on cue when cold. usually due to old brake fluid. review when fluid last changed. may be due. cycling vibration probably pads making contact. cylinders in calipers may be sludged and due for service also.