Hi, I got my panther when he was about 2 1/2 months old and he shed right before 5 months. Hope this helps. Maybe gives you an idea of when. It was very fast when it started.
What type of cham?
My veiled sheds pretty often lately and she is about 2&1/2-3 months old.
When they are growing a lot they shed more often and once they are adults every 6 months or so.
My panther chameleon has shed twice since I've had him. I would say about once every month, and will slow down to every few months once he hits adulthood.
My Panthers didn't get their first shed until about 2 months. Now they are all about 3-5 months and they have been shedding every 2 weeks.. but as someone already said it is all about the rate of growth.. the faster they grow the faster they shed.