There are several possibilities: You are not booting into a runlevel with X (a graphical user interface) enabled, or the X server isn't starting up.
First of all, try running this, which should start up an X login session whichever runlevel you are in:
Or, you might also be able to tell Fedora to start the X login manager using this:
/sbin/service gdm start
If that doesn't work, take a look at the X server log file; it will probably be called /var/log/Xorg.log. There may be error messages towards the end of the file.
The start-up runlevel may be configured in /etc/inittab; look for a line labelled "initdefault" near the top. Having said that, some newer OSes use other methods, so it may not be there at all.
If it is just configured not to start up, then you can also try this to re-enable X logins at boot time: