My H "TRIED" to act normal. We all saw through it because he went from one extreme to the other.
The staying away for weeks, I experienced that! My H would not contact any of us for weeks and then act like it was a day or too. He would argue that he just saw us and we would look at each other and knew he had lost his mind!
Anything can trigger MLC. The trigger for my H was when his mother died unexpectedly and was cremated the same day and we were on our way there. None of his brothers got to say goodbye. He took a nosedive then. I really think he started a few years before that though when he retired from the military. But his moms death sent him over the edge. I really think that if it wasn't for that he would have managed to make it through without full blown MLC.