Before answering, I have few questions like What is your height, weight? How long you have been practicing running? Do you start with warm up and end with cool down? When do you feel heavy on your legs while doing running or when you end it?
Next Steps
You should do proper warm up and cool down.
You should start with brisk walking for few days to strengthen your muscles.
Then you should do slow jogging before progressing to running.
Ensure that you use appropriate running shoes.
Health Tips
For further evaluation and guidance you need to consult a Physician or Physiotherapist. You can avail consultation in person or through video call.