I am developing web application using (C#) and (ASP.NET Web API) and MS SQL 2008 R2 and hosting on IIS7 in Windows Server 2008, All APIs return data in JSON

When i call any API from any web browser and refresh the page to call again before the first call finishes it give me warning in the event viewer and after 0 to 5 minutes the worker process in the II7 stopped for about 2 minutes(hang) and all APIs calls from all users at the period...