Recently I have observed this behavior on SharePoint servers without Internet connection
Issue:
Randomly, you are experiencing performance issues when navigating to a SharePoint site
Resolution:
1. Download the following CAB from Microsoft website http://www.download.windowsupdate.com/msdownload/update/v3/static/trustedr/en/authrootstl.cab
a. Unzip the CAB on all the SharePoint Servers
b. Install STL file
Or