34 yo female, fit and active. no medical history to speak of. sudden nausea hit with rapid heart rate while in car today. lasted for 1 hr. anxiety?

Tachycardia: It's possible that it was anxiety but it is also highly likely that it may be SVT or supra ventricular tachycardia, which is not uncommon in young women. It may never happen again but if it does recur, will need to see a cardiologist. If it happens again, try bearing down for a few moments or submerging your face in cold water to stimulate the vagal system to shut down the stimulation.