Grimefighter locking computer

After doing a routine Windows 10 update on my Samsung Ultrabook, upon power up Grimefighter starts and puts my computer to sleep. It it not accessing the hard drive so is doing nothing. I can’t even get to BIOS when powering on it just goes to Grimefighter. I stopped using AVAST a few weeks ago and to my knowledge have never user Grimefighter. Any advice would be welcome.