sometimes laptop undergo shut down from alt+f4

dear sir ,

                  there is a very serious problem occuring in my laptop ,in my laptop i m using window 8 so there is a short cut of shut down  by shot cut key(alt+f4)  but most of the time it does not shut down using it,niether shut down nor restart and when i want to put it in sleep mode,it even does not go to sleep mode.please consider it&reply to it urgently.