iMac crashing after log in.
Hey guys
I came home from work today, started to download a file from dropbox, and my iMac crashed. Locked up and restarted itself, now i know it isn't related to the file i downloaded, as i know the file and have it elsewhere.
But not i am on a continuous look of log in, crash restarts itself, log in etc...!
I have tried to reinstall OS over the top of current and that doesn't work, and i really don't want to do a clean install or Time Machine install...
Any ideas, i can boot in safe mode, but only BT keyboard and mouse and they don't connect in safe mode and am a little lost as to what i should be looking for anyway...
macOS Sierra (10.12.4)