Chosen Solution
How can I ’re-energize’ my Mac to the original normal speed?
Most likely a hard drive I/R cable issue. This is a know issue on certain models; Apple will even replace some for free but we need to know your exact machine to be certain.
Upgrading the RAM and HDD to SSD drive will make your Mac like brand new again. And cleaning also may help like deleting or transferring file to another drive. Make sure your HDD/SSD is not full this can affect your Mac performace.
