Slender Man Behavior

(No idea where I should post this so I apologize in advance is this post is not where it should be.)
Anyway, I'm new to the fandom, and while I have done some research regarding slender man, I mostly forgot about him until recently when I watched a slender man game play on you tube. My interest was rekindled, so now I'm getting more and more immersed in the slender man mythos. One of the things that fascinates me the most is slender man's behavior toward his enviroment and the humans he comes in contact with. I have no idea what his motives are, why he does what he does, and what causes him to stalk people. Could someone kindly shed some light on this?

It depends on the story. Most of them actually, at least from what I've seen, tend to like keeping his motives hidden since it sort of augments the whole fear of the unknown aspect of him.

Most stories have him anti-confrontational until the climax of the story, others don't have him do anything at all, and others make him into an aggressive eldritch abomination.
I think the initial behavior is best, as it builds tension and what he'll do next might be totally alien to the main character.
A vibe of unpredictability, if you will.

I think one thing you will soon learn is when it comes to Slendy almost nothing is set in stone, From one story to another Slendy acts and sometimes looks different.(Some story's have Slendy with a hat.)

Agreed. Slendy is by definition a subjective character- if the author decides he does something, he does it. For example, in the original SA thread he stalked kids and burned evidence, but by now he stalks everyone and often has very little to do with fire.