Slow bash startup
The most likely culprit is that you have bash completion enabled.
uninstall the bash completion package -or-
rename /etc/profile.d/bash_completion.sh to bash_completion.sh.bak -or-
manually review /etc/bash_completion and comment out sections you don't need
http://stackoverflow.com/questions/15536212/slow-load-time-of-bash-in-cygwin
Review your .profile or .bash_profile items. You can rename these files to .bak and open bash again to see if it opens quickly. If it does, remove certain sections until you find the culprit.