EDIT: This solution just worked for a day, then the system freezed again but i'm trying the method that the user almusaka sugested in
his post.
Hey guys!
I had the same issue and I think I solved it. I've been testing it for almost 2 hours and everything looks fine.
I've played games, tried Final cut, Photoshop and many, many websites on Safari. No problem so far.
This is related to AMD cards (I guess), so if you have a NVidia card it wont work.
What you have to do is navigate to the folder
/System/Library/Extensions look for the kext
AMDRadeonX4000HWServices.kext and remove it from there. (It's better you make a backup of it just in case it doesnt work you put it back in place.)
Then open
Disk Utility, select your Mac's volume and click on
First Aid > Run. Once it finishes you restart the system.
If it worked for you let me know.
I'm running the latest High Sierra update, 10.13.4