my conclusion would be that Russia are desperate to inflict damage on Ukraine now using precious stocks of missiles that they cannot easily replace because the situation is so dire for them that they're approaching the point either they use them now or it won't matter in the long run because they'll have lost anyway.
That's my reading of the situation too. If Russia had the stocks, they would have used them to terrorise Ukrainian civilians. They didn't, and Ukraine scored a massive PR win by literally repairing the damage in some cases overnight, while laughing at the amount of money Russia spent on making holes in the ground.
While I don't believe that they've run out of missiles, you have to wonder at which point it will become unviable to use any more.
It looks like Russia is sending forces towards Pinsk in SW Belarus. I do wonder at which point will Ukraine choose to tactically blow up Belarusian facilities to send a message, safe in the knowledge that Belarus cannot realistically do anything with their armed forces against them. But again, this shows the inability of the Russian command to understand Ukraine: putting forces into Western Ukraine is asking for trouble from the locals who are much, much more nationalist than those in central/southern Ukraine.
Now Russia appears to be throwing kamikaze drones at places like Chernihiv. Do they really not understand that such small attacks are going to do nothing but annoy the West, who will pledge more and more equipment as a result? Ukraine is heading towards having a fully functioning Western air defence system, which is exactly what Russia doesn't want from a military perspective.