MacBook turns of after few seconds during startup

Hi, My Macbook turns off after app. 10 secinds during startup.

I did a lot of google on this, and can see different suggestions but no clear answer.

If I hold a key on the keyboard, it sometimes will start, so I was able to do a backup.

After new installation of MacOS it has the same error, so it must be a hardware error.

I can see that a lot of suggestions point on the keyboard, and I could try to replace that, but I cant see a guide for this here.

Anyone with the same experience og a suggestion on what to do?

Thanks,

Henrik