nad 375 bee it takes morethan a minute to switch on

hi.... can any one here help me regarding the problem of my nad 375bee integrated amplifier 3 years old purchased in audio affair. the problem is it take to long to switch on about one to two minutes especialy in the morning.if you press the switch on the led light is from amber to red and blue after morethan a minute. once the amp is on it worked properly no problem at all. thanks......