Macbook air won‘t stay on/turn on normally.?

The power button won‘t work on my macbook air but when i do the combination of them (shift, command, alt, power button), it turns on but shuts right back down
(Not positive if thst was the correct combination since i‘m not looking at it right now.. but that specific type of combination).

?2018-11-07T21:17:22Z

sounds like bad power, or short on the board.
either way, expensive.