dashcams inherently want to record if they are getting power and have a working memory card inside, only if you manual have stopped a recording will you have to start it again.
Some cameras can appear to be recording judging by LED flashing and so on but dont actually record due to broken memory card most likely, but newer models will sound a alarm if something are wrong.
No matter what it is always a good idea to put the memory card in a card reader and have a look at the recordings on the computer. ( some dashcams come with a little USB memory card reader )
It take me about 6 minutes to look over a 128 GB memory card, doing this i focus on the first and last recording in a drive session or a days drives if i had several stops.
I then make sure the camera have started to record where i would expect it to do so, and likewise for the last recordings stop where i would expect them to, so in my case first file are most often me setting off from the back yard where my car are parked, then i often stop at the same gas station a few miles away - set off from there again, and then go to any of 5 or so regular destinations like my sisters place - my mothers place ASO.
I just make sure the each of the files i inspect can launch when i double click on it and my computer play it with its default video player in my windows 10, so i only watch 5 seconds or so of each file, you cant watch it all cuz that would take as long as it took recording it.
Inspecting the memory card every 1 - 2 months will be just fine, i do it a bit more often as i put bad drivers i encounter on youtube, on the other hand i only do about 3-5 hours of driving every week, cant afford more as a early retired Dane.
If your home computer are one of those Apple things, you will probably have to format the memory card in the camera when you return the memory card to the camera, this is due to those computers leaving some hidden files on the memory card that can trip up the operation of the dashcam.
When new you will probably look at the footage you have recorded often, but that soon fizz out as you find out what is recorded are the same you saw while driving, and if nothing happened then the recordings are so to say just "garbage" footage.
Many new people to this want to save everything they record, but why do that if nothing interesting happened, it will just be expensive in computer storage space.
Personally i save about 10 minutes every month of the bad drivers i encounter and want to shame in public. and that is out of the 8 dashcams in my car,,,,, yes i know thats a lot of cameras, but i do a little testing for some brands so it suddenly add up.
ATM i have 4 cameras on my windscreen - 1 camera on my mirror filming the cabin - a camera in each side, and finally a single camera in the back window.
For normal non addicted or otherwise deep into things people, a single front camera will be fine, and a camera in the back too just about bullet proof.
you dont have to film the guy running into you, your camera document what you do, and if you do nothing wrong in regard to the traffic code, well then surely you cant be to blame for what might have happened.