Why does my mac restart when idle?
So, here is the jist of the situation which itself isn't a problem, just more of an annoyance and has me wondering why.
I have a 2015 MacBook Pro, and if I let it sit idle and then wake it up it either does one of two things:
a) Returns me to my password screen so that I can log back in or, and this is the question,
b) Wakes up with both my name and a guest account option that makes me think the Mac rebooted itself as, after I log in to my account, it has to reload the whole operating system.
Why does it do this? I see no need for the computer to restart itself 3 out of every 5 times this happens and I am wondering if I could either have a problem or if this is just something normal that I have to get used to.
Thank all of you so much!
MacBook Pro (Retina, 13-inch,Early 2015), OS X Yosemite (10.10.2)