This is to do with IIS and .Net web apps. When you first hit a .net webpage (.aspx) IIS needs to compile that application into an application pool. So it is this initial compile of the application that is adding the extra time.
Note: After 2 hours of the application being inactive, i.e. none of the web pages being request it will drop out and upon first page request will need to compile, so this is why you may see if being slow at the start of the day.
Nothing to be concerned with, default behaviour. It is possible to change the timeout values etc. if required.