You can wake up the OnePlus 6 very quickly from standby by activating a useful function: Double-Tap to Wake. Where this function is located on the OnePlus 6 in the Android settings is explained in this article:
Double Tap to Wake option
1. Open the settings
2. Navigate to "Gestures" and select the entry
3. In this submenu you now see "Double Tap to Wake Up"
4. Activate the function by setting the slider to "active". If now your OnePlus 6 is in stand-by and the screen is switched off, this can be activated by tapping on the screen twice quickly.
You now know how to activate Double Tap to Wake on the OnePlus 6.