Please help... can't logon - countless dots are entered

When coming out of sleep mode and when prompted to enter my password: I try to enter my password and the the computer types countless dots (it's like there is key stuck or something) and i can't stop it. Then the logon part of the screen starts shaking super fast after the countless dots have been entered automatically. I have already taken this to apple and they gave me a new keyboard and said there are issues with keys sticking. Now i have a new key board and its now doing the same thing six months later. Its entering (discrete password dots) repeatedly until I power off and restart. I've tried "switch user" and "cancel" but continues to do the same thing. How can I resolve this issue? Thank you!