The neurobiology of this is incredible, nuanced and complex, as is the human condition. And, as you would probably anticipate, childhood trauma plays an interesting role in this experience.
Why is it that showing up, raising one's head above the crowd, or being seen following that inner evolutionary impulse within us, has us hiding?
PSA: Full disclosure: I'm only starting to fully understand this phenomena inside a more 360 degree lens. The insights this far in have helped me better understand my own self, and as such, I figured they may be worth sharing with you, here.
That innate evolutionary impulse
Within each of us is an evolutionary impulse that wants to create. A deep yearning to pursue an area of interest that at moments, makes us feel expanded, congruent and alive. Shortly thereafter, it all falls away as we start entertaining thoughts of what it might feel like to be seen.
If we are entertaining thoughts like that long enough, it can quickly shift into a feeling of overwhelm. A state that can make our current status quo, feel far more desirable, then pushing through that comfort zone to enter unfamiliar territory that our heart longs for.

Longest lifespan, least amount of threat
I reckon I have been in that exact spot about 196x before. At surface level, the part of me that wants me to be safe will concoct all sorts of intelligent evidence to support my decision of moving away from being seen.
The mind is exceptionally talented at keeping us small, and thus safe. The evolutionary design of us humans has us hard wired for taking the routes that provide the longest possible lifespan, with the least amount of threat. Important and necessary - we have this evolutionary design for good reason.
When childhood trauma is in an individual's past, there are other variables influencing this performance. In this article, we look at 6 of those variables.
Legacy programming that brings
implicit memories,
to a trauma effected nervous system
The thought of entering Unfamiliar Territory.
typically produces overwhelm
with impaired brain function unable to support in self-regulation efforts to dissolve the overwhelming feeling.
Let's start with Legacy Programming installed in-utero through to age 5
Legacy programming, a term I use to refer to the early childhood programs installed in us from in-utero through to age 5, when the brain is now considered, fully formed.
Between the third trimester in-utero and age 5, your primary caregiver(s)' stress levels, their ability to face and recover from hardship, as well as their own stress compass, was handed down to you as the imprint for your brain's formation to follow. At the same time, the experiences of your early years were directly involved in continuing to shape the formation of your brain, including it's: wiring, communication channels, and function, or the absence thereof.
That legacy programming includes explicit and implicit memories.
Both types of memory are forms of long term memory, carried in your unconscious self and recalled in a nano second, with no effort on your part for them to appear.
Explicit memory is when you can recall the experience you had in the basement, aged 5.
Implicit memory (aka automatic memory, unconscious memory. associated with our right brain) is the memory we use to ride a bike or use utensils. It is non verbal and void of content or language.

Healthy and integrated or trauma effected and divided
When there is trauma in early childhood, the brain's ability to integrate is in varying states of impaired to severed, leaving the human with the inability to integrate explicit and implicit memory, among others.
Integration is an incredibly important function of the brain for aiding us to enter unfamiliar territory. safely.
With unfamiliar territory in particular, we need a healthy brain to integrate all sorts of sensory information that is received accurately, filed in order and placed in all sorts of locations within your physical self.
We require this so we can maintain order, continue with flexibility and equip us with the necessary innate skills to efficiently assess and process any environment you are in. Having access to this, means we can prioritise and organise our way through it.
When you are physically unable to integrate, an Implicit Memory (often from a traumatic childhood experience) typically emerges as the most available input to use to now asses a 'threatening' situation. The Implicit Memory is often signalling that this outcome is a lot like a past traumatic childhood experience, and the alarm bell is raised.
That implicit memory is experienced as a feeling in the body that can quickly move from a sensation to an immersive (overwhelming) experience.
Danger is often the assessment made at this point. The body, in response to the danger, fills with chemicals to prompt your human to retreat. For the most part, we have no conscious awareness of what is happening.
We just know that we've had an "ahah'! moment, felt an expansive alignment before some stray thoughts wandered in, that we would entertain long enough to shift us into a feeling of overwhelm.
And because childhood trauma effects all areas of the brain, including the brain stem - the part of us that turns on when self-regulation is called for, the brain stem is not able to help us self-regulate and we remain in a state of overwhelm.

Overwhelm is not child's play
In many cases, a period of recovery from overwhelm is needed to bring some form of regulation back to us. For individuals with trauma recovery can look like abnormally long need for bed rest, addictive behaviour, and the need for isolation.
If we have an unpleasant experience a few times over, we learn to avoid these situations in future. In this particular case, we end up creating even more distance between ourself and what we truly want to do.
For me, it is easier to see how people in situations like these can observe the current undesirable comfort zone to be more appealing, than pursuing that moment of clarity we just had a little while ago,

So - why does being seen, having us in hiding?
I would suggest, a large part of the reason why is a result of the impaired brain/body infrastructure not able to:
receive accurate information,
asses it in a balanced form,
or process and place unfamiliar territory into its rightful place within the body.
Our body sets out to respond as per a healthy person, but because its impaired, the body's pursuit of order, instead produces chaos in the body.
That innate evolutionary impulse doesn't go away
That evolutionary impulse wants to create.
It can be ignored or we can continue to disconnect from our body so we feel its prompt less, but it doesn't go away.
I believe, it remains present, patiently waiting, without judgement, for the time to come when we can turn into it.
Often, the pursuit of personal development work can support us in:
reconnecting mind and body,
replacing legacy programming with optimal programming
that allows us to feel safe to co-create, with and through, that evolutionary impulse.
Perhaps that impulse remains as some invisible prompt to help us do The Work that allows us to pursue the work that feels more like play.

References:
Bessel van der Kolk - The body keeps the score.
The Late (great) Barbara Marx Hubbard - Evolutionary Impulse
Beethoven - his life's work, his struggles, and his own personal struggle with mental health in the pursuit of his own evolutionary impulse.