First and foremost, whenever doing any kind of exercise, only do things that are comfortable. If at any point, you feel pain, adjust your position to relieve yourself of that pain. With any type of movement, repetition is good. The following are categorized by body part.
Find a comfortable chair and sit with your feet firmly on the ground and posture upright. Keep your shoulders relaxed.
For your core and legs: tighten your abdomen and slowly raise your knee towards the ceiling. Feet should still be parallel to the ground. Alternate lifting legs and squeeze your thighs. So, we are marching while we sit. Do 5 lifts on each side. Take a 30 second break and repeat two sets of 5. Remember to tighten your abs and thighs when you repeat. Every week, increase the number of lifts until you do 20 on each side.
For calves: start with your feet on the ground. Keep your toes on the ground while lifting heels. Do 5 calf raises. Take a 30 second break and repeat two more sets of 5.
For arms and shoulders: lift arms straight in front. Slowly bring them to your side. Then bring them in front again. This is like a big clapping motion with your arms extended out. Do not hyperextend your elbows. Do 5 slow, claps, using your arms to do the motion. Take a break and repeat two sets of 5. If you need more resistance, hold an exercise band while you do the exercise.
For neck: With posture straight, and shoulders relaxed, slowly tilt head towards right shoulder. Count to 10, then tilt the head slowly to the left side. Hold for a count of 10. Repeat twice. Then bring your head to center. Place hand on forehead, and press face into hand. So, we are doing a movement forward with the face and using the hand as resistance. Repeat 5 times.
If you have pain or mobility issues, always check with your doctor or physical therapist before attempting exercises. Be safe, but keep moving.