Steve:
Where you're nervous you constantly fiddle with your hands, twisting your ring around and picking at your nail polish. Steve will take one of your hands in both of his, causing your attention to turn to him and then he will reassure you that everything is going to be okay. Then he'll give you a sweet kiss on the cheek making you smile.
Bucky:
You are a rambler when you get nervous, you will be sitting down with Bucky on the couch and start rambling about whatever's worrying you. The more panicked you get the faster you will talk. Bucky will stop your rambling by kissing you in the middle of a sentence, this distracts you from your train of thought and letting you catch your breath. Then Bucky will pull you in for a hug and rub soothing circles on you back.
Pietro:
You just get really tense and stiff when you are feeling nervous and Pietro aims to bring out the exact opposite type of behavior to your life. He will take you out to do something ridiculous like, have a snowball fight or laser tag. At first it feels ridiculous, but eventually it helps you relax and the stress starts to wash away.
Loki:
When you're nervous you do your best to hide it and act as normal as possible, eventually though you will lose focus and zone out for several minutes. Loki will notice and pull you over to the couch and sit down pulling you to lay down on the couch with your head in his lap then he will sit there and run his fingers through your hair while allowing you to tell him all about what's got you on edge.
Clint:
You are a compulsive cleaner when you're nervous, honestly you will take clean dishes from the cabinet and wash them again just to have something clean. Clint will notice and pull you away from whatever you're cleaning and towards the stereo. He'll put on some quiet music and pull you into his arms. The two of you will still there swaying to the music until you have started to relax.
Thor:
Thor knows you're nervous because whenever you're sitting down you will be constantly bouncing your leg up and down. Thor will put his hand on your knee giving it a comforting squeeze to bring your attention to him. Then he will start cracking terrible jokes until eventually you can't help but laugh hysterically at him.
Tony:
You throw yourself into work when you're nervous, trying to solve every problem that you can and this just turns every day nervousness into more stress. In these situations Tony will pull you away from work, pour you some wine and give you a shoulder massage. He definitely knows what he's doing with his hands and you will feel so much better afterwards.
Natasha:
When you're nervous you can't focus on anything, you'll try to read or do work but won't be able to. Nat will notice this and sit down on the couch and pick up whatever book you were currently reading, then she would start reading out loud to you. Her voice was incredibly soothing and hearing it put you at ease.
Wanda:
When you're nervous you have a tendency to bite your nails, which you always hate. You've mentioned how much you hate this bad habit of yours so she helps you deal with it. When she notices that you've started biting your nails again she sit with you at the table and paint your nails. It relaxes you and the bad tasting nail polishes helps you stop the bad habit.