I am having anxiety and don't know why. What can I do?

Get help. If you can find a quiet place - do so. Breath in slowly ; deeply through your nostrils. Fill your lungs with air (but not to the point of discomfort). Hold for a count of five then slowly begin to exhale through an open mouth. Repeat at least 12 times, longer if you need to. If you haven't been assessed for your anxiety - that would be prudent. Anxiety is no fun but it is treatable.
Get checked. Reminds me of car making strange sound and I don't know why. Generally in these types of situation, best to bring car to mechanic and get it checked. Delay and ambivalence tend to be driven by fear of bad news. No one wants to learn car needs major repairs. Avoiding the issue might resolve the anxiety. If that does not work, get checked by a doctor.