I've made some previous research about this and all I've found is either very old or related to the rendering cost of the scene (lights, polycount and so on); In our case we have a pretty simple scene in terms of rendering cost (just some 3d texts, 2d sprites, a few unlit shaders....) so I don't think our issue is there.
We are working with Unity 2018 and deploying the app in a Samsung S8. We have about 50 trackers in the scene with very simple augmentations and no heavy-loaded Monobehaviour Update. It works in VR mode with the Vuforia SDK. The app works pretty smoothly at the beginning but after about 10 minutes the device is seriously overheated, the tracking starts working poorly (we guess it's due the overheating) and a short after that the device closes de app. and pops up a warning window with a 'app. closed due to overheating' message. This happens even if, after playing a few minutes with the device, tracking a few markers, we let the device aside with the app still running but tracking and rendering nothing.
As I said we cleaned as much as possible our updates (at this point there is no update running when we let the device aside), removed all lights and anything that could be expensive to render. This gave us a better overall behaviour but the device is sill overheated after some minutes and, eventually, closing the app.
Any idea or recommended Vuforia setup to prevent this from happening?