how to stop chrome from self launching on iMac

On the off chance you have the Bing redirect adware installed, run Malwarebytes for Mac.

1. Launch Google chrome, if not already running
2. Right click (use two fingers to click) the Google Chrome icon at the dock (the bar at the bottom of your mac)
3. Hover over "Options"
4. Uncheck "Open at login"

Hope it helped!

You need to supply more details. Chrome doesn't self-launch on its own.