13inch. It has happened many times. I tried to reinstall Mavericks, Yosemite, El Capitan and Sierra, but it still crashed. It happens randomly. When i watch videos on Youtube, play music on iTunes, or use Logic Pro X, it freezes and restart automatically in a few seconds. And I also ran AHT, but it passed. What should I do? Really need help. PS: I am not a native English speaker, so my English sucks.