Why does my very new laptop sometimes shut down by itself?

See above

Maybe activated in the energy saving mode

Yeah, but it turns off while I'm watching a movie

Hi. Counter question: Why do you think a question without any detailed information can bring you the information you want?

What kind of details would you need

All. Brand, model, operating system, programs used, battery charge status, when exactly does it happen, with which application, after which period of use.

It is best to add a question.

I watched the movie on Watched with a rather low battery