Don’t think it is that he has no interest in doing it. He would be equally happy (if not more so) to succeed at the negotiating table. Were Russia to invade, their military (even based on the current build up) is far superior to that of Ukraine and I don’t think there is any doubt as to the eventual victor in that scenario. The real motivation is likely to be Putin’s overarching ambition to see the restoration of the former Soviet Union as a major actor on the geopolitical map. Putin has made much of the threat, as he sees it, of Ukraine and other former Soviet countries joining NATO (ironically the actions of Russia are the very thing that will drive other countries to join NATO) but that is not the real end game, as far as I can see. Think Donbas could be taken irrespective of Ukraine as the fighting has continued much of the time.
Notwithstanding the progress of the current talks, it will be interesting to see what happens after the Beijing Olympics on 20th Feb (as he won’t want to offend Xi Jingping by launching an invasion while that is ongoing). March will also be the last window of opportunity because they will presumably want to launch an invasion on cold, hard ground rather than April onwards when it will be more difficult.