Hello, we are finishing up a 4 year campaign next session, and are gonna start Curse of Strahd soon after. Everyone seems to have solid ideas on what they are playing but im struggling finding something. I normally play a "lawful-neautral good character" or characters who are very Han Solo in nature. 
My DM said it'd be best if I kinda changed my vibe for this one. Which i get. 

So id love some recommendations (mainly class and subclass) but story connections to the world with as little spoilers as possible would be neat. Thanks. 
Party Comp So Far- Soul Knife Rogue, Fiend Warlock , Shadow Sorcerer, and Life Cleric  (The fiend warlock says he is melee)

Yeah, CoS can be very deadly, you don't want to be a reckless character, it's also pretty morally grey so lawful-stupid will get your character killed. Looking at your party you could use some more front-lining as well as more healing so Paladin would be pretty good fit, but I would go for one of the more morally grey subclasses, Conquest, Ancients, Vengeance would all work well IMO. Watchers would also work if you are willing to have them question their oath.

Ranger could also be good, as Wisdom skills are probably good to have. Tasha's Beastmaster (I'd suggest a wolf theme), or Swarmkeeper (I'd suggest spider or raven theme) are good. Gloomstalker would be kinda depending on the darkness from your Shadow Sorcerer buddy since there isn't a lot of dark dungeons in CoS.

Moon Druid is another option.

It’s not strictly the strongest subclass but Alchemist Artificer in gothic horror campaign is classic. Gives you some healing, you can fight from afar with a hand crossbow that launches “wooden stakes” for flavor and gives you lots of solid skill options.

CoS is trying to capture classic gothic horror themes, so maybe look at games like bloodborne for inspiration, the ill fated hunter who hunts in the mist and slays abominations.

as for classes, the party look a little light so fighter or paladin are solid options for front line options to support the team

The Monster Slayer Ranger is a good yet often overlooked subclass.  It works well if you want to go with a Van Helsing type character.

This shouldn't be too spoilery, but the premise of any Ravenloft campaign is that you are from a world outside the Shadowfell and then get abducted by the Mists. Not sure if your group will run it that way, but that is the default. So unless you are really pumped to play as Abraham Van Lincoln, I'd suggest making a character for whatever world you are probably going to start out in, and then roleplay their reaction to being transported suddenly to a strange and terrifying world.

Seconding the suggestion of a better front line. Echo Knight or Psi Warrior could help a Fighter play into the theme of weirdness. Beast Barbarian could be thematic as well. Plenty of good Ranger options have already been mentioned, and they're probably more thematic anyway. Still, a hefty battlefield presence is going to sway things in the party's favor. Although, then again, it sort of depends on how and how deeply you want to explore the theme... Good horror explores the theme of powerlessness, and if you were going to play into that, you could choose something flashy like a Swords Bard so that the party's weaker front line becomes a feature of play. Is the group cohesive enough that they could shift play styles in order to deal with having to scatter and regroup?

Paladin. You will up your party's chance of survival by choosing something classically tough. And just because you're a Paladin, doesn't mean you have to be lawful good, Paladins come in all flavors.