MacBook Pro will not turn off

I have a MacBook Pro, 2.5 Mghz, I7 chip. I have El Capitan OX10. My problem is it will not turn off. All the programs go off, and I get to the wallpaper and it just stops. I have tried to update the programs I use, and when it's up, the computer is working well. I put it in safe mode, then back to normal; after that it turned off, but only once. Any advice or answers would be welcome. Thanks