User1065476709 postedHi AlanOliveira,
The application pool needs time to build the libraries before it can begin processing them. This can be speed up by using some kind of script. It also depends on whether you're using a website or a web application project.
You could also looking for IIS Auto-Start feature and setup it on your server may help speed up the process. By default Application pool gets shutdown in case of user inactivity default value of 1740 mins. You can also disable idle TimeOut by setting to 0 can help a lot.
Best regards,
Sam