Yes, try an AHT first, that sounds like a good plan.
After such a freeze you could also open the console app and then look under 'System Reports' if you find any kernel panic logs from the freeze. The error in such a kernel panic log could help to google for a possible reason of the freeze. But in most of the cases the informations in these logs are only helpful for engineers at Apple.
Then start Disk Utility and execute "First Aid" on your system partition to scan/repair for file system errors.
After my bad experience in the last days (red in my previous posts) after a SMC and NVRAM/PRAM reset I kind of hesitate to recommend you this. But SMC and NVRAM/PRAM reset are normally the first thing that people recommend in forums like this in cases of strange system behaviour. But if you plan do so, make sure you have an actual backup just in case!
You could also try to boot once in Safe Mode since this will not only check your file system again, but also completely rebuilds the kernel caches. Because of those tasks macOS did when booting in Safe Mode such a boot needs a lot of time, so be patient. A corrupt kernel cache could be the reason of such freezes, but who knows.
Here is an overview from Apple to all those needed startup key combinations for rests or Safe Mode:
Mac startup key combinations
Since I have this update only installed such a short time and not yet experienced any system freezes I can't say if your freezes could be related to this update or not.
