sciatic nerve pain

I have just woken with a burning sore cramping pain from my waist down my right leg. this is a normal occurance at the mo. and presume is the sciatic nerve, this pain goes approx 5mins after getting up and sitting in my chair. I shall now be able to o back to bed shortly. I think this happens or is so intense because I lay on my left sidebut dont fully relax my side to lay on the matress thus causing a tension to occur, a bit of a catch 22, tension causing pain, pain causing tension.