my 1999 corvette makes a squeaking noises when i first start it

On the LS1 engine there are two belt tensioners. One for the ac and the other for the main front end accessories. You may have a bad tensioner and/or a bad belt. With the engine off see how easily you can twist the belt. If it feels very loose a tensinioner is bad. You can also watch the tensioner while the engine is running to see if its moving too much. Its hard to explain online how much is too much so if you need help from a shop here is a link to find a shop near you. https://repairpal.com/repair-shops Alex

It's a belt that's making the noise - upon engine start up - the alternator is working a little bit harder to replenish the battery's charge that was taken out by *cranking* the engine - that puts more stress on the belt - after a few moments - battery charge has been restored - less stress on the belt - noise disappears.