4 year old anxiety

Hi, how sad!
What causes her anxiety and how does she express it? Can you elaborate, maybe give an example?

We are struggling to identify what the trigger is but she will get very clingy, sad, and pukes she's so nervous. An example was we stopped at gas station to get milk and she had a panic attack that we didn't get gas and were going to be stranded somewhere even though we had plenty of gas and never have been stranded

Oh, what a sweet but sad little worry wart!
It may not come from you; she might have overheard something. There is so much on the news about the energy crisis, on food that runs out, on the climate, people are talking and she might have overheard something. These times are hard and a child is easily impressed, and even often right to be concerned.
The thing is that her concerns are real; they should be addressed as such. If she can feel these things and reason about them then she should also be open to a solution. Try to reason with her. You could try something along these lines:
"I can see you are upset. Can you tell me why?
...
So, you're upset about not having any gas and getting stranded. How would you feel if we got stranded? Let's talk about what we would do in that situation.
...
You're upset, that's okay! You have the right to be upset and we accept it.
...
Being upset is a pain in the butt though, right? It's nicer to not be upset. But if you are upset that's okay. If you want to try to not be upset that's okay too. Let me know what I can do to help, we are here for you no matter what."

Does this help a bit?

She may also be one of the children/people who are super sensory . Or sometimes called hyper sensitive. Investigate this area of research and they will give you a picture of what is included in this label and why it’s impt to ID those who have this.

Yes, that's a real thing. The trick is to handle it well and help the child live with it instead of playing it down or turning it into 'being silly'. There are good sides to it, too!

I had OCD from the age of 4 buy never knew it. Instead of taking me to a Dr. my parents abused and neglected me. Take her to a Dr. or professional right away. Get to the root cause asap. I'm so glad you'll being so vocal about it now. Great job!

We won't know for sure what is going on with her until a professional sees her. She is only four though, she's a little girl. In my opinion it's best to wait until a professional sees her. She may be absolutely fine, it may be a phase.
Be real with her, give her real answers and find solutions together. And please let me know what happens and how it's going.