Same issue occurred to me 2 days ago. After about 24 hours of discovering my wordpress admin panel looking like it was in some sort of ‘safe mode’ like the example above, I was notified that my site contained malware and/or malicious code. I submitted a support ticket and was informed that my site had been hacked.
I’m in the process of trying to recover and restore my site.
There are several active threads over the past few days reporting of this problem. It looks like many wordpress sites are being targeted.
My suggestion is that you have a look at your site logs to see if any files were modified recently without your knowledge.