I have ehard of you and seen your vids, good job for being good with so many characters.
but meh, I think your sheik could use some work, please take this as criticism and not an insult
for example, you should approach with a bair, at least against snake. even though sheik outcamps snake, the snakedash thing is kind of annoying. if you are afraid of being sheild grabbed, space the bair so you don't. you may be ftilted or utilted, but you can usually bait one of those, then punish accordingly.
i know that sounds sort of gimmicky, but try it. rar'd bair, soft hit or sweet spot to ftilts, to a utilt
also, against snake, you should be very aggressive in the air. the only aerial that snake has that is really dangerous is his bair, but as long as you stay in front or below him, it is no threat. go crazy with your uair (good range) and you can even get a uair > second jump > another uair. when snake is using cypher offstage and you are at the edge, it is basically a stock right there. just be aggressive, go down and fair him, he can't do ****. you can even do bair if your fair is too stale (if its too stale it doesnt get him out of cypher). don't be afraid to fair him a million times, it is a very good move because of its trajectory
you use the needles well, but you should charge them more, and stop wasting full storms in the air lol. i usually only use air needles to screw up some of my friend's recoveries (like peach).
anyway good stuff, knowing how good you are at other characters, sheik shouldn't be too hard.
snake is a very fun matchup to play imo. you can be very aggressive, but also have to be careful at the same time, since snake can kill you underneath 100 EZ. utilt is sex, use it more, it is your "all purpose" move on the ground.
dthrow is good, you can follow up against snake with a uair or a bair. if he airdodges sheik can punish him easily.