What is a word for someone who tends not to think too deeply; often about life, themselves or the world (something more neutral than "shallow" or "oblivious")? Perhaps my difficulty is that i personally don't think that not thinking is a neutral characteristic. Plus, the type of person i am trying to describe does not necessarily take life with ease or serenity. The word i seek is more about thought-life, than temperament. A non-thinking person can still have a negative, angry, unpleasant (etc.) outlook on life, they just don't question it.
I'd say such a person is happy-go-lucky
A happy-go-lucky person does not plan much and accepts what happens without becoming worried.
It implies that they are carefree and accept life the way it is.
Carefree is a viable option that I use myself.
[a : having no worries or troubles]
She has a carefree attitude toward life.
Unreflecting is defined as "not engaging in reflection or thought" (here). Unreflective is a variant that works nicely for what you want.
Easygoing comes to mind. I think it captures a facet of the meaning you specified.
able to stay calm about things that anger or worry most people
[American English, Cambridge Academic Content Dictionary]
relaxed and not easily upset or worried
[British English, Cambridge Advanced Learners Dictionary & Thesaurus]
One might expect that a person who does not tend to think too much about life, the universe, and everything would, in turn, tend to be less opinionated, less stressed, and less confrontational than the average bear, i.e. easygoing.
- of a happy lighthearted character or disposition - lacking due thought or consideration"
Here's a somewhat neutral or even positive term for the type of person you describe: pragmatic.
Pragmatic 2 : relating to matters of fact or practical affairs often to the exclusion of intellectual or artistic matters : practical as opposed to idealistic - M-w
How about "aloof"?
removed or distant either physically or emotionally MW
Philistine: "A hollow gut, full of fear and hope that God will have mercy!"
phlegmatic - self-possessed, calm, or composed.