You may be having postural hypotensive episodes and the heart is compensating by beating harder to pump efficiently. Also, please get your blood work done to see if you may be anemic, since lot of vegetarian diets miss adequate iron. Anemia can cause palpitations as well. With your history of ablation surgery, it would be wisest to call your doctor about any new symptoms of heart. Good luck!
It would be a good idea to discuss with your doctor relative to the past treatment you have had, and in general.
You didn't give a number for what your resting HR is and what it changes to when you get up from resting. I'd say if the numbers were something like 65 and 80, I'd not think much about it. But if 65 (just a number) and 130+ I'd be concerned and want to get it checked.