When should i need to worry about palpitations? had 6 or 7 in a row got nervous for sec. lasted about 6 seconds. i have been going to the gym now and doing cardio more?

Once in a while palpitation is usually benign but if it occurs often you should have a formal physical exam with basic blood test +/- 12 lead EKG. You should make a diary of each palpitation period such as your activity and time when it occurs, any unusual trigger such as drinking high caffeine drink or emotional feeling, etc. However, you can still continue with gym exercise in the mean time.