The hallmark symptom of POTS (Postural Orthostatic Tachycardia Syndrome) is an increase in heart rate from the supine (lying down with the face up) to upright position of more than 30 beats per minute or to a heart rate greater than 120 beats per minute within 12 minutes of head-up tilt.
When you stand up from sitting or lying down your brain sends a signal to your heart to beat faster and more forcefully to compensate for lower blood flow to your brain. This is called the autonomic nervous system. Sometimes this response can be not enough, or too much, but it sounds like what your describing is well within range. See your doctor if it concerns you.