I've had my MacBook for 3 years and have never had this issue... Recently (maybe a month ago?) Messages and soagent are making my CPU spike. It sounds like my MacBook is about to take off into outer space so I have to kill both processes in my Activity Monitor. That fixes my issue, temporarily, until I open Messages again and it starts all over. I've tried researching this but don't really seem to find a fix.
I'm running Mac OS Sierra, v 10.12.6
This is driving me insane... any suggestions?