That behaviour is classic when the battery or supercaps totally fail.
When you power down they are there to 'properly' close the last file.
What you need is a program that can close an open file.
Try changing the boot delay to 5 seconds. There are quite a few ignition sources that are temporarily killed off by the starter motor.
As a test test the unit indoors using a mobile phone mains charger.
If that works OK then the dashcam isn't faulty.
Also, does your car have stop/start ?
There are many fuses that temporarily lose power when the starter cranks. If you're wired to one of those then you almost certainly will have problems. You need to find an ignition source fuse that doesn't lost power during cranking.
Normally a tedious job...
I've performed many tests both day and night and for me HDR causes more pseudo motion blur.
I prefer to have maximum clarity daytime footage and night will be what it is.
All my testing screenshots are on DashcamTalk.
I'm not convinced with high endurance cards.
I've been operating a A119 V2 and subsequently a V3 with the same Samsung Evo Plus 128Gb without issue since 2018.