I do really big stretches before I even get out of bed (yes, just like my dog!). I just started a sun salutation yoga stretch (not in bed) for about 5 minutes as well. Makes a big difference for so little time! Very easy to wake up with as well.
Everyone is different. I have sciatica and a herniated disc. I do stretches, arching backwards and holding 10 seconds. Then leaning forward, I take hold of my calves (if I’m able to bend), and hold 10 seconds. Repeat.