If I am absolutely sure it isn't pain, fear of falling or some other obstacle that we can potentially alleviate ... I am fairly direct in my approach. (yes, as you know, these patients are out there ... I've had patient walk unassisted into an ED treatment room and ask for a bedpan 5 minutes later)
"What are you having trouble with?"
"You are free to move about and set up the room however it's most comfortable for you ... just so that we can still get to you to provide the care that you need."
Sometimes it's a *blank* look or surprised look from me -- "what has changed in your symptoms in the last 5 minutes?"
that encourages appropriate independence.
You'll have to find the wording that works for you.