IIS - Other - Web application performance issue

Hello.

I have a custom ASP.NET web application. It is .NET 3.5 application with AJAX controls deployed under IIS7 on separate application pool. It has waiting indicator. Indicator starts immediately when the first statement of the application in the Page_load method is executed. Indicator stops when calculations are over. The problem is when application loads. It takes about 30-40 seconds for the first time (that "first time" is about 2-3 times per day) to load. In that "first time" white screen in browser area is shown about 30-40 seconds. And after that indicator starts. Indicator regularly takes about 5 seconds and then results are shown. When i open the same web form after, lets say, 30min, the white screen doesnt apper, just indicator as i want. As i understand application pool is recycled regularly by IIS. After recycling the white screen is shown again for that long time once. I tried to turn off automated app pool recycling. But it didnt make a sense. So what is happening when that white screen takes place? Loading some internal DLLs or smth? How to avoid such a long loading?

Thank you very much for a help.