Pimax has a standby mode that activates after a period of time where the headset is not moving. This is 3 minutes by default. When this triggers, all controllers and trackers will power off. (This may do other things as well, but I have not confirmed anything else.)
Disable the pimax standby timer
Open the JSON file located at %LOCALAPPDATA%\Pimax\runtime\profile.json, and change the setting for standby_timeout_min to 0. This setting is the number of minutes until standby mode is activated. 0 will disable this altogether.