Let me give you a little bit of the background as to what is really going on here long term.
Russia, like any other major player on the world scene, wants to preserve and/or expand their influence. That can be done either with threat of "hard" power (military solutions,assassinations and other skullduggery) or "soft" power (influencing via economic arm-twisting and such). Putin, to his credit, has been spending his years at the head of the Bear trying to convert Russia into greater use of soft power and less threats of hard power. And that's not easy, since Russia has been historically about as subtle as a sledgehammer vasectomy.
But with their vast assets of natural gas, and Europe's unending thirst for it,...Russia seeks to be as exclusive a supplier of natural gas to Europe as can possibly be attained. Not only for hard cash profit, but to have sway over European nations' policies via having the hand on the tap that can shut it all off. This resulted over time in the NORD STREAM pipeline under the Baltic Sea, delivering LPG from Russia to Germany. Russia and Germany are currently attempting to complete NORD STREAM 2,...and this is something Uncle Sam really, Really REALLY wants to NOT happen.
Part of the whole Ukrainian mess is because the U.S. had been trying to out maneuver Russia's aims by helping their next best competitor in the region as an alternative for Europe;...Ukraine and their own gas production. Russia saw that this was likely to be successful unless they were able to control, manipulate or steer Ukraine themselves. It's a little hard trying to get your nation to focus on producing gas and serving the market with it if Russia is invading you. But,...if Russia went too far,...that would potentially trigger a much larger war which nobody wants (even Russia),...so they just took the Crimea and have kept tentions high and things generally unstable. Just enough to keep Ukraine on their heels but not enough to require NATO to respond.
Meanwhile, under both the Obama and Trump administrations, the U.S. has been levying sanctions on Russia and Russian companies to try to stymie the NORD STREAM 2 project. The U.S. has even been levying sanctions on any company of any nation that in any way contracts on the project. Many Swiss companies have been trying act on the project due to their slightly greater economic independence thanks to the banking center of Geneva, but even they are getting hammered by a State Department that has tentacles globally. The U.S. has been rather effective is its interference. The pipeline was to have been completed in late 2019, but now is almost finished.
And this is why Russia is now rattling it's sabre on the Ukrainian border again.
Merkel is about to end her final term as Chancellor, and there is belief that the U.S. (CIA) will do what it can to ensure a better and friendlier person attains the position. With the completion near,...if the U.S. is to somehow sabotage things, it has to be now. We know it, they know it,...everybody knows it. So Putin is making it clear that he just might make Ukraine pay the price for whatever Sammy does here in the next few months.