Lexus GX serpentine belt squealing

[Chun99]

I have a 2017 Lexus GX 460 with about 90k miles. My car has been making a squealing noise ever since i had replaced the serpentine belt. The noise would last anywhere from a split second to a few seconds, and it would only happen when you start the car first thing in the morning and won't happen throughout the day. So basically the car needs to sit over night for the noise to appear. Another mechanic told me it might be due to the aftermarket belt so he ordered an original one and replaced it for me and it was still doing the same thing. He told me the next thing would be to replace the pully and the tensioner but he said the noise does sound like it's from the serpitine belt but doesn't know why it keeps on making that noise even with the original. Any insight would greatly be appreciated.