I've said from the start, "If Biden is elected, he will be out of office by Easter." The three most likely ways he will be shown the door is a) Removed via the 25th Amendment, b) Resigns due to a scandal, or c) Resigns due to "health issues."
And the signs are all there. Pelosi was talking about the 25th Amendment option even before the 2020 election. The other day this article came out, Dozens of House Democrats Call on Biden to Give Up Sole Nuclear Launch Authority. Of course Kamala is already handling the President's duties interacting with foreign leaders as well. Old Joe is not helping things when he does things like his "stable Jesus" kind of speeches either.
Now, the article is couched with the quote, "The worry is not about Biden, but more about Trump or another future Trump-like president..." but the reality is, why are you worrying about a possibility 3 years in the future? They're not. They're worried about right now.
Now the good news.
We have (or at least had) a "no first strike" policy. IOW, the only time the US would launch our nuclear missiles would be as a response to an incoming nuclear strike. The fact that we are moving away from that policy to "consider the first-use of nuclear weapons in a wide set of circumstances" is terrifying. Here's more on it and the process.
I seriously hope that if a president even considers a nuclear first-strike the 25th Amendment would immediately be invoked. There is no scenario where if we opened that can of worms, we could not expect a nuclear retaliation from somebody.