Virus or Windows 10 junk?

[Montego]

To my Friends at Tom's
I had to go somewhere so I placed my desktop computer in SLEEP mode. When I brought it out of SLEEP my log-in screen came up (normal) but up in the top left corner were the words "RIDDLE ME THIS" proceeded by a small circle with an upside down U in it (some sort of symbol, I think) none of which IS normal.
So the questions are; has anyone else experienced this; and does this appear to be some sort of virus or could it be just some more Windows 10 junk?
Thanks in advance for any help given
Montego

 

[dexxterlab97]

Can you post a screenshot so I can take a look better. It could be a malware (unknown program of some sort) or it could be Cortana. Some site showing Cortana making some sort of riddles.

 

[basroil]

Disable lock screen suggestions/ slideshow and check again. If it comes back, you might have a virus

 

[COLGeek]

Have you scanned for malware/viruses? I am completely unfamiliar with any such app (of course, there are bazillions of them).

 

[Ralston18]

Not something I would expect at all via Microsoft/Windows 10.

If it is a link: Do not click!

Run your AV software/Malwarebytes etc. immediately.

Then think about any recent downloads, updates, sites visited that may have slipped in some sort of hijack.

Check for some new, unrecognized process or service being started at boot up., May provide a clue.

 

[Montego]

This appears to have been a one time incident.
At around the same time that this strange line ("RIDDLE ME THIS") appeared, a few of the sites I visited started to freeze-up and I also started to get LAG on one of my video games (Diablo III), which would get worse as the play session increased, time wise
Accepting the advice that some of you provided I ran an anti-virus scan, a temperature check, and a complete battery of troubleshooting tests.
The results indicated that I did not have any malware issues; the CPU and GPU temps were checked at an ambient temp of 24C using the HW app and showed that after a minimum of two hours of gaming my CPU = max 41C and the GPU = max 47C; and troubleshooting revealed that it was the Adobe Flash 'Accelerator' that was causing site freeze-up and game LAG.
I still have no idea what caused the original problem but it seems all good now.
Thanks again for your help and I hope I can return the favor.
Montego