Feeling heartbeat fast sometimes without doing anything

A sudden increase in heart rate while at rest can be due to anxiety, caffeine intake, dehydration, or lack of proper sleep. In many cases, these episodes are temporary and harmless. However, if they occur frequently or are accompanied by dizziness, chest discomfort, or breathlessness, it should not be ignored. Monitoring triggers like stress or stimulants can help, but a medical evaluation such as an ECG may be required for clarity.