I updated to Catalina 10.15.4 this morning, and in the 2 hours gap I was using it, I already had to restart my computer 3-4 times. It just shuts down, sometimes with a woof of air. (English isn't my maternal tongue sorry for the mistakes)
I had to restart the update too, about 3 times, because the computer was shutting down by itself while making the update (!!!) That should have made me think twice about persevering with the update...
I've been bottle fed by MacIntosh, than Apple practically since I was born, and I never ever encountered this kind of problem. It actually getting on my nerves because this kind of crap never happens with Macs!
MacBook Pro (16-inch, 2019), 2,6 GHz Intel Core i7, bought on Christmas 2019.