Intermittent error when calling WCF service: "Failed to establish secure channel for SSL / TLS with authority"

I am calling the svc endpoint every 5 minutes. The problem is that sometimes I get this error:

"Failed to establish secure channel for SSL / TLS with authority"

And in other cases, it just runs successfully without any problem. As it is so random and intermittent that I cannot find the root cause.

Does anyone know what should be causing this?