It is possible that feeling a heightened heart rate at rest could be a side effect of starting a new medication, such as for anxiety or mood. It is common for certain medications to cause transient increases in heart rate or feelings of intense heartbeat, especially in the initial stages of treatment. Monitoring any other symptoms and discussing any concerns with a healthcare provider is recommended. Typically, these effects should diminish as your body adjusts to the medication, and the benefits of the treatment should become more noticeable over time. If you have any further questions or if your symptoms worsen, do not hesitate to seek medical advice.