My macbook was okay after I opened it while holding ALT+CMD+P+R, and this apple support page explains how to do this procedure : https://support.apple.com/en-ca/HT204063
That was it for me, they told me it was because I didn't turn off my computer often enough...
So if you haven't tried it, it can't hurt. If it doesn't work, then you can move on to another explanation...
Hope your computer is ok!