What is the name for alliteration that begins with an s?

There isn't a specific name for alliteration that begins with the letter "s". Alliteration is the repetition of consonant sounds at the beginning of words, regardless of the specific letter.

For example, these are all examples of alliteration, even though they start with different letters:

* Slippery snake

* Pretty pony

* Big blue ball

So, you can simply call it "alliteration" even if it starts with an "s".