Nissan maxima 00 AC belt squeals for a moment and

it can be one of 2 things, its either the inside of the belt (the side in contact with the pulleys) has glazed over causing it to slip on the pulleys giving you the squeal or something along the belt line is loose e.g. the alternator, water pump and so on also causing it to slip from the slack in the line, if thats the problem you just need to tighten a few bolts or replace them if its the belt being glazed over you simply need a new belt

this means your belt needs to be tightend, if its not at the proper tension it will squeak at low speeds, especially when you first start your vehicle, and if you turn on your ac.