I met a performance issue when using the WCF service.
Here\'s the story:
I wrote a self-hosted WCF service which is hosted by a console application
One way could be to add your own warmup script; a script that calls your service on initial load.
Though, this answer might help you, usually, the first access to the service is slow, but the consecutive accesses would be within a sec or two.
The first slow response is related to the JIT compilation of the service assemblies; which means its normal.
Alternatively, you may want to Profile you app. Also you may would like to checkout this article that I wrote some time back.