Sounds like a mechanical fault to me, possibly a power stage within the machine going intermittently faulty or the screen unit itself at fault.
I'm assuming when you say the screen is shaking you mean physically vibrating?
Or do you mean there's just visual fluctuations?
In the latter scenario, that's likely a hardware fault as well but possibly software.
If the machine is only six months old it will still be under warranty so if I were you I'd contact your supplier with a view to a repair under warranty.
Unless you're absolutely convinced it's a software fault of course, in which case it's your problem, not the suppliers.