I was not on Methadone for very long because I had the same side effects as you Dame, come to find out though my doctor actually had me on a high dose compared to the medicine he had me on. He switched my morphine to methadone 1:1. One of the members here mentioned that was too high of a dosage.
I found that sitting still watching tv was bad, I'd fall asleep. I only drove once and it was the last time I did that, I almost fell asleep at the wheel. Fortunately not all people experience the same thing we do. Some have little to no side effects at all and that is fantastic for them. I only wished I could of taken it because as you mentioned it was the most successful medication I ever took.