When you use because, you are firmer about the reason and it's the most important part. On the other hand, since/as are milder! Also, as/since generally go at the first place and because in the end. Well, I don't say that, BBC does! :)
Here it is:
Because is used when the reason is the most important part of the sentence or utterance. The because clause usually comes at the end.
But in the other cases, it's well-known and thus, less important -
As and since are used when the reason is already well known and is therefore usually less important. The as or since clause is usually placed at the beginning of the sentence.
If you ignore the question formation, you may straightforwardly ask with a different structure:
Is it possible for you to use a wired connection because WIFI seems to be unstable?
Or, if you love 'since,' informally you can ask -
Since WIFI seems to be unstable, is it possible for you to use a wired connection now on?