It happens to my Note 9 sometimes, started just a few weeks ago, maybe once or twice a week.
The other problem I've noticed is that when the display is off, pressing the power button twice doesn't work or works only to turn the camera app off and takes you back to the display on showing the lock screen or just turning the display off, like you never pressed the power button!
It's not to a point that it bothers me, but I'm just worried, since I've grown accustomed to bring up the camera and take pictures or videos very quickly since the GS6 edge, that if I get into a situation where I need to take a picture quickly and this issue happens, I won't be able to use my phone's camera!