Hello , even i am faceing the same issue on my 16inch MBP ... i think i have been facing this issue after i updated to 10.15.5 and still i am having the issue on 10.15.6 ..... Did you resolve issue ??? is it a Software Glitch ????It happens to me on my MBP 16" Cataline 10.15.5
Unlocked the screen and keyboard and mouse are totally unresponsive. Been this way randomly for quite awhile. This time, I hit the Siri button which caused it to become responsive again. For what that's worth.
Tried disable Power Nap , SMC reset , NVRAM reset but NONE HELPED ..... ONLY WORK AROUND FIX i have been able to find out is that if I TURN OFF THE WIFI BEFORE PUTTING IT to SLEEP IT DOES NOT HAPPEN .
again it's annoying everytime to turn off the wifi before Sleep ....
Please any HELP WOULD BE APPRECIATED , Please Help ...
Apple Support seems to have no clue about the issue