Lower back pain just from standing around

Hi all,

I wanted to ask about some lower back pain I've been experiencing.

Usually, it's when I've been standing around a bunch (or walking).

I don't have any issues if I get on my bike, go to the gym, have a full workout, etc.

It might just be a "things need to warm up" kind of thing, or possibly a postural thing.

The back pain itself is more of a discomfort/dull pain, and leaning over forward to stretch it out feels more intense than the back pain for a moment, but kind of relieving too once I stretch into it.. kind of like if you've been looking to one side for a long time, and you turn your head to the other side just to move it around.

Is this a sign of bad posture that I need to address, lest I create permanent damage to my spine over the next 10 years, maybe from naturally over-arching my lumbar?

p.s. I've scheduled an appointment with a PT, but wanted to get the hivemind's perspective too.

In general, I have some amount of hypermobility (most noticeable in my shoulders, which dislocate super-easily, if in a precarious position like attempting an overhead squat), and some knee pain... I wonder if that's all linked, or if this is separate... It'd be good to know if there's an overall thing that's exacerbating this, or if the back issue is isolated.