Stiffness is often a protective signal from your body. When you are still for a while, especially with poor posture or low muscle engagement, your brain starts to guard the area.
Again, this is not because you are fragile. It is because your system is trying to help. It just might be overdoing it.
Move a little, often
You do not need a full routine. Just shift positions regularly.
Change the story your body is hearing
Every time you move without harm, you are reminding your system that movement is safe.
Be kind to yourself when stiffness shows up
It does not mean you are doing something wrong. It just means your system is still learning.
If sitting still stirs up your pain, it is not because your body is broken. It is because your system needs more variety, more gentle motion and more safety signals.
Even small movements, done consistently, can ease that cycle of stillness and stiffness. You do not have to do more. You just have to do enough.