Configuring the new instance of SSRS (SQL Server Reporting Services) , i have observe that when you first time click on the SSRS reporting site it takes longer time to load sometime forever. Once it is load one time than it would be good and no issue. If you close the session and reload everything first time it takes again longer time.
I have load balancing in Reporting server so i thought it was taking longer time but after reading online material and applying following change on IIS - App Pool setting , it resolved the issue.
Select the second tab - Performance and there is setting of the App Pool, Shutdown worker processes after being idle for (time in minutes) : 20 mins. This is the default setting.Unchecked that, and you should see the performance improvement. On a site you which runs slowly you can see the direct improvement right away. It may require to restart IIS service.