HELP plz. My keyboard is typing indefinately number "8"

[parasa]

When I turn on PC, everything seems normal. After some minutes, when I open a chat window, or try to open a browser, starts typing number "8" indefinitely. Every time I have to restart PC in order to gain some time with normal typing.
I opened the keyboard, cleaned it and even used another keyboard, but the problem persisted. I guess it isn't a keyboard problem.
Can u think of something to help me?

P.S: (My keyboard is a wireless Logitech K870 and the other i used is a cheap no name USB Keyboard. My OS is WIN 10)

 

[webworkings]

If this is doing this no matter what keyboard you use, then there is probably something on the device that is the cause. Malware, virus, etc. You would have to do some good deep scans with programs for the different types of files to make sure there is nothing on the computer.