This article explains how to fix a Terminal.app it the event that it starts to take a very long time to get to a shell prompt? For example, the window opens, blank, and just sits there for like 10-15 seconds until the shell prompt comes up.

To fix this issue you need to delete everything in /var/log/asl. In order to do so you need to run the following commands using an administrative account. Start with:

cd /var/log/asl

sudo rm -rf * 

Enter your password and Terminal should now load the shell prompt immediately again!