Solved ......PC very slow after 1 day with new 2080ti



Revert those settings back. You might have set the speed too slow or turned it off altogether. That would cause CPU to overheat and stutter.
 
How about GPU temps? RTX cards are primarily constrained by temperature. Mine ran at 74c with out-of-the-box overclock and hit a high of 1920 MHz and settles in at around 1850-1875 MHz after fully warming up.

I upgraded to 2080 ti from gtx 970 also and the mistake I made was to not uninstall drivers. I thought it would be ok because both cards were nVidia. I don't even think the instructions in the box said to uninstall old drivers. As a result, I had weird things going on with the GPU and several crashes and a system freeze once. Did you use DDU? This card is different architecture, so I would say to anyone use DDU by default before installing any RTX card. Follow the instructions on DDU download page exactly and do it in windows safe mode with your network disconnected just to be sure. Then reinstall the drivers. I downloaded the driver install file from nvidia before hand and only reconnected to network when nVidia asked me to log in (some don't even install Geforce Experience, so you may not have to login).

Also, make sure your game/gpu is not set to oversample. You can render at higher than screen res with this setting and it will eat up gpu resources and lower fps. Not sure if this applies because seems like your system is lagging even on just the desktop?