I’ve Google’d this problem, but all the info I find refers to an error message (I get none) or multiple reboots (I don’t have them).
I have an Intel mobo with all the sp2 plus patches on it. I just got the notice to install sp3. When I run it, it moves along properly until just after it sets a system restore point and starts processing. The computer just powers down as if I had pulled the plug. It restarts (because bios is set to do that) and then complains that the installation was interrupted, and then deinstalls itself. I’ve also disabled antivirus and other apps and tried downloading the sp3 file and running it from my hard drive with same results.