I'm facing an issue of heating my rog 2 is heating when im not using the phone its temperature is like 37 degree
37C(I assume) is fine. You don't need to worry until it's getting around 45C-50C.
For an idle temprature when you're doing nothing, that's pretty high. For me when the room is cool-ish the temprature stays at around 26-30 on normal use and around 32-34 when my room is warm.