Identifying cardiac abnormalities has mainly been determined by the observation of electrocardiogram (ECG) signals. To collect ECG signals, it is often necessary to place ECG electrodes on the body for critical analysis of ECG data transmitted by such electrodes. By analyzing this collected data, it is then possible, for example, to examine the intervals between the heartbeats (or R-R intervals) to measure the heart rate variability (HRV). However, this process requires a multilayered setup for both hardware and software which can be costly and time consuming. To overcome these challenges, we introduce in this paper a real-time millimeter-wave radar-based, non-contact vital sign monitoring system that is capable of detecting the heart variability rate without the use of any heart rate sensors or wires required. Through this system, it is then possible to detect any heart rate abnormalities by analyzing the collected data. Throughout the paper, we present results for three individuals and compare our approach to heart rate monitoring devices and Apple Watch.