Have you undervolted your card at all? I had a similar issue with my Sapphire NITRO+ RX 5700 XT, and through a process of trial and error I have estimated that I was undevolting it too aggressively. For example it black screened more than 60% of the time during the launch sequence for Doom Eternal.
I ended up adopting AMD's AutoUndervolt feature in Adrenalin (20.4.2) and it has been stable ever since. I also reboot straight away each time I touch anything in the Performance (e.g. old Wattman) section as I find it is quite fragile.