Uh, if you have to go back 15 years to find a point where a country isn't invading it's neighbors its going to be super understandable that in the past 15 years countries have wanted to join a defense alliance.
Keep in mind, the USSR only collapsed in 1991 so the question you're asking is what aggressive actions has Russia done in the first 26 years of it's existence to make other countries scared of it.
Of which you have Chechnya (~1999), Georgia (~2008), Ukraine (~2014).
Before that, it was the original WW2 formation of the Soviet union with invasions of Finland, Estonia, Latvia, Lithunia, Czechoslovakia and so on and so forth (which was obviously the whole reason for the existence of NATO).
The WW2 and postwar period wasn enough to sway e.g. Sweden to join NATO. Nor were the Afghan, Chechen or Georgian wars. It took the Ukrainan war to really see the veil come off.
But in this entire period I don't think there is much in terms of annexations by NATO countries, or countries currently in NATO but before the formation of NATO?
Not sure what your comment above really tries to say? Is it "I don't understand how countries in Russias vincinity can be afraid of annexation by their imperialist neighbor, they only invade a country every 5-10 years that's not so bad"? Are you hearing yourself?