You have TMON installed.  It's a debugger.  That's it's icon that is the last icon you see in your startup screen.  If everything is ok, you should be able to get out of it and back to the Finder by clicking on the words ExitToShell in the second screen you show.  I don't know why you are falling into TMON at startup.  Usually it is activated only during a crash.  Maybe something else is causing you to crash, and TMON is getting activated by that.

TMON is in your Extensions folder, probably in a folder called TMON folder.  If you remove it from the Extensions, TMON won't load.  However, you might consider keeping it there.  It can be very useful.