A resting rate around 100 may simply be
sinus tachycardia, meaning the normal pacemaker is beating faster because of a trigger. However, the ECG is needed to distinguish that from rhythms such as frequent extra beats, SVT, atrial fibrillation/flutter, or less commonly other arrhythmias. The
American Heart Association overview also notes ECG plus tests for thyroid disease, anemia, and electrolyte abnormalities as part of palpitation assessment.
Until assessed, avoid energy drinks and excess caffeine, nicotine, alcohol binges, and non-prescribed stimulants; hydrate normally. If possible, record the pulse during symptoms: rate, whether it feels regular or irregular, duration, trigger, and any associated symptoms. This makes ECG/Holter interpretation much more useful.