>>I assume no files were modified on the app root directory? Even changing permissions can initiate a recycle....
>>
>>This *might* apply if it's IIS7 : http://support.microsoft.com/default.aspx?scid=kb;EN-US;950573
>
>This seems to be a bug in the way IIS 7 handles a new compilation.
>
>I have attached the image.
>
>You will see that at 06h00 is the time of the recycle. Thus, it might take a few minutes before the four worker processes gets loaded based on the access to the site. You see those four entries at 22/10/2013 06:00:35, 22/10/2013 06:03:35, 22/10/2013 06:09:35 and 22/10/2013 06:14:35. You can see the worker process ID represented by 588, 3332, 6512 and 6544.
>
>Then, I sent a compilation at 11h15.
>
>Records 22/10/2013 10:50:19, 22/10/2013 10:50:47, 22/10/2013 10:50:58 and 22/10/2013 10:55:13 will show the unloading of those four worker processes. This is the started up time and at the right the shut down time.
>
>But, there wasn't any traffic on that Web site until 22/10/2013 11:16:18 which then triggers the loading of new worker processes.
>
>But, the bug is with record 22/10/2013 10:50:12. I never had such notification before. This should not even be there. This is an additional log related to the unloading process and the proper unloading process is logged a little higher in the image.

This: http://stackoverflow.com/questions/2010479/asp-net-mvc-app-restarts-itself/2010530#2010530 suggests a virus scanner as a possible cause. Also suggest disabling FileChangesNotification in the registry - but that sounds a bit drastic :-{