Intermittent page load delay

Hello,

Experiencing this rather odd issue, users have been complaining lately that when accessing our site every few refreshes are extremely delayed 10seconds-30seconds. Sometimes it it's OK for a little while, sometimes its not.

Our network team on-site says no issues, firewall team says no issues, etc. The only thing I've heard back is that it appears that for a few reloads it behaves normally, and then intermittently the following HTTP request(s) will delay on obtaining/setting the cookie (ci_session i think).

Any ideas? I've been going crazy the past week!