Site on self signed cert loads slowly on mobile Safari

I have a site using a self-signed cert (not live environment). On iOS Safari, the site loads very slowly over https, over 40 secs.

But it's fast over http.

What could be the issue? Have already accepted the cert upon prompting by Safari

Have tested on iPhone 6 and 6S+

Chrome and desktop Safari is fine on https as well.

Solution

I've run into this exact issue recently on our site. This does not appear to be reproducible with other mobile (Android) devices. If you have an internal certificate authority (CA) with which you can export a root CA certificate this is the easiest way I've managed to correct that problem:

On a PC:

Export the root certificate .cer file from your CA and save it somewhere handy
Email it to an account that you can access on your iOS device

On your iOS device:

Open the email you just sent and click on the attachment, you should be prompted with a wizard to install the certificate. Click through any warnings you get about it being untrusted, etc until it succeeds
Try to access the https site again and it will appear as a truly trusted connection, hopefully with less of a delay/lag.

Here's a walkthrough for reference: https://support.quovadisglobal.com/kb/a64/how-do-i-install-a-digital-certificate-onto-an-iphone-or-ipad.aspx