Screen goes blank. After about half an hour the screen turns of,. power light still on, battery

Question

After about half an hour the screen turns of,. power light still on, battery light still on, wireless light still on. Pressing any keys on the keyboard does not bring the screen back on. press the power button and laptop turns off, press the power button again and it goes to the password screen, when the password is put in it returns to the same page when the screen first went blank.