'Hot-desking' is a common working practice, for example in call centres.
If you share your desk, readjust your chair and desk before you start work.
If you normally work at the same desk, then you could install a DSE checklist on your screen or pin it up and follow it before you start work.
You should be able to spend time getting your desk set up properly in your employer's time, not be expected to come in early to make it safe and comfortable.
Just One More Click: Doggy drama about staying safe online at work.