My notebook often suddenly turned off without i press the shut down button..what caused it ?

Question

and what should i do?

Answer 1

It could be crashing due to it overheating, so you always want to keep/use it somewhere where it will have a good airflow (not on carpet/blanket etc.)

It could also be a hardware issue, the best thing to do is make sure your battery is on securely.  If you have any more problems with it, I would contact the manufacturer of the notebook and let them know what's going on.  They will most likely take care of the issue if it's still under warranty.

Answer 2

it is overheating. Probably it is full of dust and the air can't circulate. Try cleaning the dust. If that doesn't help then buy a laptop fan or use it in a cool/cold places. To learn windows OS hacks and secrets go to my profile.

Answer 3

power saving options maybe set, or was running on battery power and has drained, more on power saving below