The symptoms you are describing I have been experiencing on and off for the last 8 years. Prior to starting medication i couldn't sit down long enough to eat a meal and if i wanted to watch tv i would often do so stool up. Like you i just didn't know how to sit or put my legs. I use to sit with my legs hanging over the chair arm to try and get some relief. The symptom you are describing is restless leg syndrome(RLS). The symptoms of RLS are often transient in Parkinson’s and so may be confused with other symptoms of Parkinson’s such as akathisia (restlessness caused by drugs used to treat parkinson's) or when the effect of drugs used to treat parkinson's such as levodopa wears off requiring intake of further medication. Also, RLS may cause night-time pain which may be mistaken as arthritis in Parkinson’s. Furthermore, RLS is treated with drugs such as dopamine agonists or levodopa, and people with Parkinson’s who develop RLS may already be taking such drugs.
I was prescribed an iron supplement which has helped. The dopamine agonists are particularly good for treating RSL. It sounds to me that you probably need your drug regime reviewing and either you dosage increase or possibly another drug introduced. I found walking and exercise relief the symptoms of RLS.
Speak to your PDN or consultant and tell them you think you're experiencing RSL.
I am now able to sit and watch tv and eat meals but i do notice sometimes if i'm a bit late taking my meds, due to the meds wearing off i get this sensation come back along with dystonia but this eases once the meds kick in.
Please see this info sheethttp://www.parkinsons.org.uk/pdf/FS83_Restlesslegssyndrome_0308.pdf