MacBook Pro 2019 keep on restarting after random keyboard problems

You're doing all the right things but it's still not working.

Are you in England or Wales? If so, you're protected by the Consumer Credit Act for six years. See:

Legal - Apple Products and Consumer Laws in the United Kingdom - Apple

This entitles you to a free repair or replacement from Apple. They should be able to preserve your data if necessary and you ask them to do so!

Try using an external keyboard assuming the laptop is able to boot and the issue is just a bad built-in keyboard. Even try Safe Mode if a normal boot doesn't work.

If you can boot the laptop, then immediately backup your data.

I don't recommend spending any money to repair any 2016-2020 Intel Mac with USB-C ports for multiple reasons. The money spent on repairs is much better put towards a new laptop.

FYI, 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. People should always have frequent and regular backups of their computer and all external media (including the cloud) which contains important & unique data. Apple makes this extremely easy by providing Time Machine backup software with macOS, but there are also several third party options as well.

Do you use the Time Machine built-in app for backups?