Fluttering feelings in the heart can be indicative of palpitations
. Stress, anxiety, exertion, and stimulants like caffeine can trigger palpitations
. Pathological condition like cardiac arrhythmias can lead to palpitations. Seek the opinion of a doctor and get an ECG done for any kind of heart problem. A clinical examination and complete work up will help in determining the cause. Do keep me posted.
Best luck and regards!