Stimulating one's private parts is biologically design to be pleasing or gratifying. Connected to positive feelings that will make you want to do it again. There are lots of nts who masturbate daily, or have sex daily. Younger children usually won't connect the stimulation with any form of sexual feeling, and it's not as unusual as one may think that little boys or girls stimulate themselves. Even kids who aren't on the spectrum. And the only people who will think it's weird are adults, because only adults think of it as something sexual.
Around the age when puberty hits, children will naturally start to hid their more private parts (a nudist lifestyle isn't as natural as they want to think). So a 10-12 yo kid would be more likely to stimulate themself in privacy or hidden, while a younger child might happen to do it in the living room because they haven't yet started treating those body parts as private even from family.
Very young children who stimulate themselves will often stop doing it long before puberty, and not even remember having done it later.
Seeing self stimulation as something shameful or wrong in children is weird. It's as weird as people feeling like they need to hide a 3yo's body under lots of clothes even when bathing in the garden. Only adult would ever connect being naked in front of other people with something sexual that need to be kept private from everyone. Children don't view each other in that same kid of sexual way, even if they do things like studying each other's genitals.
I don't think it's a bad thing to masturbate often. If one feels a need because of anxiety or stress, that might be a problem. But it's the anxiety or stress that is the real problem, not the masturbation. I masturbate to relieve stress, but that happens very rarely now that I have found ways to deal with stress and anxiety before it becomes so consuming I need physical means of relieving it. The need to masturbate may feel very intrusive, but I really think it should be taken as a symptom of stress rather than anything else.
Pure libido is of course also a thing. And I have a feeling that men may have an easier time to accept it as a natural part of being a species that reproduces sexually. Libido is a good thing. And can be awkward if it doesn't match one's partner's libido. But if it can be solved with good communication and occasional to daily masturbation, I really wouldn't see it as a problem. Libido or the lack of it are both natural variation in humans. It shouldn't be viewed as a problem that needs solving, in most cases.
But if it gets too bad, there are meds which can make libido calm down. I think I've heard that anxiety meds work for it, which kind of makes sense to me. Anxiety and excitement (not only the sexual kind) are rather closely related feelings, at least in my experience, kind of like a dark and light side of the same coin.