1998 Other Jeep Models Irregular electrical output

I have a 98' Grand Cherokee Laredo with an electrical quirk. For a few weeks, I have been getting a little belt squeak at start up (very cold weather - WI). After e few seconds, it would quiet down, and not return until next cold start up. Last week, I started it and it started normal, after driving a short distance the squeal came back and stayed present for 3-4 blocks. Then the volt meter went to 0, and the 'check gauges' warning light came on. Stopped and looked and the belt was o.k. and the alternator was spinning, but the meter still read 0. Turned it off and restarted, and it was then fine (read just shy of 14v) - ever since, I get fluctuation from the volt meter, normally either at 7v or down to 0.0 A restart seems to always correct it. For the last two days, I am getting a reading just above 14v, which has NEVER happened before. Any thoughts on what to try first? Belt is aprox 2 years old, battery is 3.

thanks for any suggestions you can offer!