If they were scared NATO was about to preemptively attack them, they probably wouldn't be moving air defense missiles out of Russia (including as far away as St. Petersburg) [1] to move them to Ukraine.

But if you really want to worry about this, you don't need to consider the current war in Ukraine. You could look at this article from 2017 that describes a long-term plan to equip the U.S. submarine missile fleet with "superfuze" warheads that can accurately destroy hardened missile silos, which completely changes the strategic balance against Russia, in a way that might make things more dangerous for everyone [2].

[1] https://bnn-news.com/russia-moves-missiles-from-st-petersbur... [2] https://thebulletin.org/2017/03/how-us-nuclear-force-moderni...