I've noticed that my heart rate changes with my posture. When I stand, it's around 105-116 bpm, sitting brings it down to 90-100 bpm, and when I'm lying down, it's 75-85 bpm. My blood pressure doesn't really fluctuate much though. So, I went ahead and got an ECG, and it showed sinus tachycardia but otherwise normal. The strange thing is I can feel palpitations in my neck and chest when I stand, but I have no other symptoms. I run on the treadmill at 5-8 kmhr without any problems and my pulse stays between 100-120 bpm, but right after stopping, my pulse jumps to 163 bpm before gradually coming down, and my blood pressure was 140 over 75 at that moment. Should I be worried about this?

Based on your symptoms and the ECG report showing sinus tachycardia, it seems like your heart rate is elevated in response to changes in posture and physical activity. Sinus tachycardia is often a normal response to certain triggers such as exercise or stress. However, it is important to monitor your symptoms and follow up with a healthcare provider for further evaluation and management. In the meantime, you can try to stay hydrated, avoid caffeine and other stimulants, and practice relaxation techniques to help manage your heart rate.