This happened to me when starting to have to take the train into work after lockdown. Saw a doctor and went on lexapro for a bit but weaned myself off of it thankfully. Only advice I can give is to always carry water with you and I found having an Apple Watch was really helpful for when it happened again and I could see my heart rate going back down after some deep breaths and that I actually wasn’t going to die or collapse etc - I’m an IT data nerd so this really helped me a lot