Circle with a line through it on start up
My iMac with 10.15.7 does not start up every time, since I upgraded to 10.15.7. About every other time I get a circle with a line through it. I have started in recovery mode and used Disk Doctor to repair and the messages said successful. With a Reset the computer boots just fine. I have reinstalled Catalina from Disk Utility. I have booted in the Safe Mood, then rebooted successfuly. I have also reset NVRAM Option, Command, P, R If I start up in Recovery Mode, and go right to the upper left corner of the screen, and do a restart, the computer boots just fine without doing anything in Disk Utility. What do I need to do to make my iMac more stable? Thanks Allan
[Image Edited by Moderator to Remove Serial Number]