Scotty,
When I startup my 2008 Yaris with 140k miles, if I have my AC turned on, the serpentine belt squeaks pretty loud for a little while. It last a few seconds. Once the car is warmed up it does not occur and the AC is fine. Never squeaks otherwise. It only happens at startup AND when the AC is on. So I just don't turn on the AC for the first 5 minutes and no issues. It this ok, or should I have it fixed. I feel like it is the serpentine belt tension because about a year ago my daughter driving the car out of town had to get a new alternator installed at a discount auto shop. Otherwise car runs great, very dependable.
Adjust the tensioner.
I'd replace the belt. If it's been slipping it's probably worn. If you have a manual tensioner be sure to set belt tension to specification. If it's an automatic tensioner, after 13 years and 140K miles it should be replaced.
