MBP Mid 2012 model.
It happens every now and then. Nothing specific which triggers it actually.
Previously, it shuts down then turns back on by itself, but for a couple of times, since yesterday I think, it won't restart back up. I needed to press the ON button to turn it back on again. And no, there are no error messages.
I'm not sure if a mid-2012 MacBook Pro would be supported by Apple anymore, and even if they do, I imagine a fix might be more expensive than it is worth given the computer's age, but you might want to contact Apple if the issue persists. Doesn't look good.