It's a baby burm. Generally baby snakes will not sit out in the open as millions of years of evolution has taught them that usually ends with them becoming food.
Like I said before, what are the temps? What is the humidity? Humidity plays more of an important role in babies as they dehydrate a lot faster than adults and as a general rule, a dehydrated snake is not going to eat as digestion takes a lot of liquid.
And how rarely is rarely for tongue flicking? I mean just sitting there they usually don't flick it that much. But now if you do any movement or anything in or around the cage, the snake should be alert as it's a baby and in an unfamiliar place.
Hate to say it but if the snake is just laying there all stretched out not flicking it tongue or seeming alert and not interested in food or responding to outside stimulus, I would get it to a vet as it sounds like it's on it's way out of this world.
