My laptop won't start up completely?

I have a Lenovo Ideapad Y500 with Windows 8.1. I turned it on this morning and it will start up, but it keeps re-loading the desktop over and over. If I click on a program, it will try to open, but then the computer will re-load the desktop and the program will shut down. This happens about every 3 seconds (even in the windows 8 screen). I've tried restarting, locking and unlocking, and checking the task manager (the only program that doesn't close down?). I have a lot of Hhomework to do tonight and would really appreciate any help I can get!

Added (1). I tried checking all of the keys and that doesn't seem to be the problem.

Check your keyboard, sounds like a stuck key, if I have an external keyboard also attached it may be a key on that. Probable enter key or one of the F keys