MacBook Pro 16" 2019 experiences GPU panic on sleep

That is probably just a temporary fix. The Logic Boards on this specific model laptop have an extremely high rate of failure for multiple reasons....GPU, memory, SSD, T2 chip.

If you are not already backing up this laptop, then you better start making frequent & regular backups of this laptop if it contains any important data on the internal SSD. If you don't have good backups, then you will lose the data if the Logic Board fails completely. There are a lot more new ways to permanently lose access to the data stored on the internal SSD of the recent Macs due to all of the hardware, software, and security changes. Even an expensive professional data recovery service is unlikely to recover any data from the internal SSD.

You should also plan to purchase another laptop because the laptop has already told you it is failing.