(Concern) Lower back stiffness

Recently, perhaps due to my posture, I feel a lot of stiffness in my back that didn't hurt before. It feels especially stiff in the morning, and on days when I walk or move a lot, I feel even more stiffness and discomfort in my back.

I moved and sat down and got up a lot, so I feel very stiff. I seem fine during daily activities, but when I do a little more work, my lower back feels tight and uncomfortable...

It's so hard to get up because my muscles feel even more tense after waking up...

What are some good stretches for the lower back? I need to do some lower back stretching.