I have problems with my iMac 21.5" -2012 (13.1 model).
The machine is not starting like normal. The fan turns on max from the begining, lasts over 6 minutes and then the system is very slow.
I changed the HDD to an SSD but it did not improve. I put macOS Catalina, Maverick, High Sierra and the results are the same.
What can I do to troubleshoot this problem?