That's a good idea. I'm getting a camera too so will remember that tip!
Before you buy consider this..
As I see it there are two types of camera..
1/ those fitted in cars that switch on and record when the engine is started, and re- record over and over on a permanent loop, so its fit and forget until you need it .. I have one and it works well!
2/ The type we might use on a bicycle, but are really action cameras that need more input to avoid a full Memory card and generally dont run for too long on their internal battery.
I find the gopro a bit of a headache because it records till its full and then stops! It can loop record, but only in set segments (30mins, 1 hour etc) so every time you turn it off, and then on again it creates a new loop so quite soon the card is full and you have to delete the files to continue.
As we are electric I have been looking for a fit and forget camera, possibly designed for motorcycles that will start recording when I turn on the bike, and stop when I turn it off, and have found this one which will continuously loop record and turn on and of when power is applied.. The camera is small and waterproof, and the electronic bits can be fitted elsewhere (frame bag etc).
I am not recommending this, its just something I have been looking at
https://dashcamtalk.com/innovv-c3/ml
If you want to helmet mount.. a gopro is a big lump stuck on your helmet if your head should hit the road. COL ( Like LOL but crying!)