Cheap dash cams are rubbish - always locking up/stopping, you never know if they are recording or not! You need to spend 3 figures for a real good reliable one. or...
I use my phone and an app called 'Autoguard' which has a premium upgrade for not much.
It's really good & can be set to background recording, means it carries on recording even with the screen lock on or other apps in use, sat nav etc.
I put mine to the LH side of the rearview mirror - high up on a decent holder.
And obviously whilst it's there doing an invaluable job -- it stays there for the duration of the journey with no touching it