Hi lama87,
Thanks for reaching out using Apple Support Communities. Here to help.
We understand you are seeing an issue where the brightness is low upon initially unlocking the device.
True Tone Display is only available on certain models. Which iPhone do you have?
Another relevant setting to adjust may be Night Shift. If this is on, you can see if the issue only occurs during Night Shift hours, or see if the issue persists after turning Night Shift off.
Auto-Brightness is another feature which will automatically adjust the brightness according to the lighting and ambiance detected by the iPhone. This can be disabled in Settings > Accessibility > Display
The resource below will cover all of these topics and more.
Adjust the screen brightness and color on iPhone
Hope this helps. Take care for now.