Random delays on opening connection to SQL Server - sql

Question

In one of our systems we experience random delays when opening a connection to SQL Server.
The system is running Windows Server 2012 R2 Standard and SQL Server 2012, located on the same physical machine as our application.
Even when our application is idle, it is executing DB operations once every few seconds on average.
DB operations our application executes usually consist of 3 steps:
open a connection to SQL server
run a stored procedure
close the connection
Normally the first step takes a tiny fraction of second, while running a stored procedure may take much longer, depending on many factors.
The problem: opening a connection may randomly take 5-13 seconds. This only happens rarely, once in a few hours, even once in a day.
In other words this could happen once per a few thousand DB operations. We have not detected any discernable pattern in the timing of these delays.
There is nothing suspicious in the SQL Server log files.
Running SQL Server profiler does not seem practical, as the fault may not be exhibited for 10-20 hours.
We have not seen this phenomenon on any other machine.

Answer 1

It looks like we've fixed the problem. Somewhere I read a recommendation to try to use SQL Server authentication instead of Windows authentication. The problem discussed there was not exactly the same as ours but somewhat similar. Since connection string is used in every Open Connection operation, I decided to give it a try. As a result, our application has been working for 3 days in a row by now and there has not been a single incident of opening connection being slow. To put this in a context, before this fix we had several incidents in 24 hours on average, and not a single incident-free 24-hour period for the last two months.