Occasionally, but depends on the artist.

I am not afraid of asking, but I do know many of my friends are. For them, commissioning is fearful entirely so it's not only asking for changes but talking with an artist to purchase a commission.

hm, thanks!

Not now, but when I was first doing commissions and asking for commissions I was pretty shy! When I'm working for a shy client now, I try to ask them to choose between two things: "do you like it better like this or like this?" and that can help narrow it down and get them comfortable with chatting!

I think asking for details is only natural, because how should the artist know if I want something if I don't tell him. In the end the artist too wants that I am happy with the art I purchased.

But mostly I always tell the details when ordering so I don't have to ask too much for changes/details later^^
And if the artist don't want me to ask any more details he/she would surely tell me or not?

relying on their friends - often not.
However, this is work and you paid for it - so it needs to be done as well and clearly as possible.

However, it is extremely rare that additional moments somehow interfere with it. The biggest creative hell for an artist is to ask every 3 / 5 / 8 / 20 hours "well, can you show the progress of the work?"

Specifically, I try to often send the stages of my work, but many people come across this type of customer.
(this does not apply to some sketches or a small amount of work, it is rather about orders that are usually made 2-3 weeks at a calm pace)

I don’t mind, however, when they ask, for example, once every 2-3 days, however, I know many artists who are comfortable doing a large amount of work once a week

Oh Ehen it comes to ask for the progress of the work I usually ask once per month. If the Artist tells me that it takes a while or if i know that the artist can not work on it every day then only once every few month.

I have a lot of friends who either have anxiety, who are afraid of confrontation, worry about upsetting other people, or a combination thereof.
Some are just worried about upsetting the artist, whereas others have had negative experiences with other artists. In both cases, that has molded their views on asking for more details, changes or corrections.
Those who have anxiety usually don't want to pass it on to others, I've noticed. I've also noticed that a lot of times they don't have much more a process than the base idea, and as such are willing to roll with the punches for the rest of the commission.
Using one friend as an example, they feel put upon when asked for their opinion (I.E., uncertain about what they want to see detailed further), or they worry that their requests might somehow insinuate that the artist's work isn't good enough. This affects how they respond, and how frequently.

It's complicated. Everyone has their own process, artist and commissioner alike.

It's always a gamble whether artists are detail-oriented or not. Some love detail, some really don't.

I like my badger character to look very animaly, but badger skull anatomy is quite distinctive, and most folks are only used to drawing dogs and cats - trying to explain that the eyes need to be closer to the nose than the ears, and that the bridge of the muzzle follows this other curve, or that the limbs are drawn twice as long as they should be... Especially if they've nearly finished the picture already, or their first attempt looks like they've pretty much ignored the reference!

As the previous person as l said - it's quite stressful sometimes.

Art is tricky because art is subjective and has an unpredictable outcome where-as physical products are straight forward. It involves bartering and negotiating, which are effectively confrontation, a trait that reflects a dominant personality and has been effectively punished out of most people.

Content also plays a part on both the artist and commissioner wanting to conduct business.

I would say, as a fellow artist, that there's a line out there but it's not easy to see at all. When is it too much? When are you being too picky? When are you pushing someone to draw "your way" and not in their style? There are other questions similar but, the answers are very hard to know... so, yes, I think there is a bit of 'fear' sometimes. But it can always be worked out when both artist and customer are quality people willing to work though those kinds of things.

I think it's your point of view that's closest to me

In the end, as the one asking for the commission, everyone should take a moment to prepare first. In many cases, it's mostly a love of the artists' style and work so, when that's the driving force behind the request, the info is generally minimal because you WANT the artist to draw their style... their way. It's why you chose them. However, if you're wanting your character drawn in a very specific manner, then you need to have ALL the info, thoughts, description... everything prepared and ready. Plus, if this is the case then... generally... you are seeking a very specific art style that you believe can capture your character exactly as YOU see it. So much more detail and, likely, much more communication both before, and during, the commission.

I make a suggestion or two, but leave it up to the artist in the end.
How the artist interprets the character(s) and seeing them in a particular art style is the best part of commishing.