I've had this problem too.
The SMC reset usually works to get the trackpad working again, but not always and sometimes not for long. It is also a pain to do when you are in the middle of something. I have also done the NVRAM reset a few times with similar results.
What seems to have worked for me (so far - touch wood) is to switch web browser and stop running WhatsApp in the background.
I did have WhatsApp starting from login. Since various members of my family use it as the main way to keep in touch it is nice to have it immediately available. However, my phone is generally close at hand too, so it is not too big a loss to keep it turned off until I want to use it.
I noticed that the trackpad freeze usually happened when I was browsing the web using Safari. This isn't definitive, after all this is probably when I use the trackpad most given the way I use my Macbook. However, it did make me wonder whether Safari was the problem so I started using Chrome as my default browser which I already had installed to access some content that was not compatible with Safari.
So far this seems to have made a big difference. Not perfect, but many fewer problems.