I'm using Macbook pro-2019 13inch with Catalina 10.15, so recently I started facing this issue, after turning my mac on from sleep my keyboard and trackpad doesn't respond even the backlights doesn't turn on, then Bluetooth search for keyboard starts and after some time my keyboard and trackpad starts working back.
I've been running into the same issue, but have been experiencing it since 10.14. I've contacted Apple Support and they had me reset the SMC, I haven't had enough time to see if this is a permanent solution (I doubt it is). There's many troubleshooting steps they'll have you try before they consider servicing the MacBook.
Here's the page with the instructions to reset the SMC Resetting SMC - Apple
My hopes are that this is a simple software patch and will be resolved soon.