You are not alone @mw31115320 and @TheSuzyQ .There are many of us that can't get into a what they call "exercise". Or there are times we can't do much of any physical activity. Exercise does do us good. But overdoing when we are "down" can be detrimental.
But "moving" can be incorporated in our lives at times. Little things can be done even resting. Not every exercise routine has to be Olympic training.
You need to remember to not move into where it hurts, but just up to there.
While sitting or resting, move (pump) your feet back and forth (like tapping your foot to music).
While sitting or resting, tap your knees together and apart (as comfortably as possible).
While sitting or resting, raise your arms up over head and down (just in your comfortable range).
When standing at the sink, you can modify those things as needed and have the counter to hold if you need to.
These are just little things to do when you can't bear to be doing anything. It will keep you moving and you might not be so stiff. And remember that your daily "have to" routine is keeping you moving also, just don't overdo that either. Always be careful. Hope this helps in a small way.