Lots of apps as well as system services may partially wake the phone intermittently to do various things like refresh data or check location. They shouldn't be doing a full wakelock (i.e., turning the screen on), but partial wakelocks are normal (where the screen does not turn on). Unless you're experiencing unusual battery drain, I wouldn't worry about it too much.
You mean those little lines? Not uncommon. Here's my graph--notice all of the brief wakes when my screen is off.
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I'm on 4.4.4--your M8 must be on some version of KitKat, right? There shouldn't be huge differences unless you're on Froyo or something.