I have these days a lot.
Some things that I have noticed though: it happens more often when I don't have much sleep; and also when I don't eat properly (skip meals or only eat a little and leave the rest); it usually comes on if I am feeling anxious about something that is completely normal for someone to feel anxious about (having to speak in front of quite a lot of people; being in public areas etc.); in some cases, I have actually induced the feeling by concentrating on past experiences when I have felt it.
So I conclude that healthy sleep, healthy eating, allowing the anxiety to some extent but try and learn to face and deal with it a little, and remember that anxiety is all within your thoughts will probably help a little.
But this is something that I have learned from my own experiences and everyone is different. For you it may be different. You may want to make a note of patterns that you may notice when you have these experiences in order to identify when you are more likely going to experience these feelings. This is the first step towards learning about it and therefore working towards dealing with them adequately.
I have a little "journal" that I keep to write my anxiety experiences down and little tasks to do in order to deal with them. I usually write my thoughts down. I then try and counteract those thoughts with more rational ones. When I have bouts of anxiety, I will go through those thoughts and it sometimes works.
My anxiety is like a roller coaster though; I can calm myself down but it creeps up on me all the time. But I would rather it be a roller coaster than having it constantly maxed out in panic mode.
I hope this advice helps you.
We are all in this together.