First of all, I suggest that you don't do a lot of strenuous exercise when you recover from a serious illness. With the gradual recovery of the body, after all aspects of function are in good condition, you can participate in sports activities like normal people.
Low-intensity stretching and warm-up activities are still possible. Grasp the strength and time, don't worry at first, and don't try to be brave. After all, you are responsible for your own health.