ASP.NET应用程序重新启动太多

I have an ASP.NET WebSite which restarts in every 1-2 hours in a day so sessions and other thing are gone and users are complaning about it, because they open a page and do something for 20 minutes and when they submit it, a nice "we are sorry" page is there.I have an ASP.NET WebSite which restarts in eve