SQL Server 2012 Connection Timeout Expired

I am running MS-SQL Server on Windows Server 2012. From time to time I get this Exception:

Server Exception : System.Data.SqlClient.SqlException (0x80131904): Connection Timeout Expired. The timeout period elapsed during the post-login phase. The connection could have timed out while waiting for server to complete the login process and respond; Or it could have timed out while attempting to create multiple active connections. The duration spent while attempting to connect to this server was - [Pre-Login] initialization=6; handshake=9410; [Login] initialization=0; authentication=1; [Post-Login] complete=5627; ---> System.ComponentModel.Win32Exception (0x80004005): The wait operation timed out at

When it happens I get hundreds of them in a few minutes and after a while it recovers. I couldn't find anything useful on the web. I would appreciate any help.

Thanks