Hmmm, I had a similar issue with discord, also an electron app, where if there was no notification daemon running discord, and occasionally the desktop, would freeze maybe running something like mako would help?
I don't use signal desktop, but I did google the issue and it seems signal-desktop regularly has issues. see this https://github.com/signalapp/Signal-Desktop/issues/2442, but there are several workaround like in this thread https://github.com/signalapp/Signal-Desktop/issues/6247
It seem signal desktop created using electron, same as VSCode, slack, spotify, etc. Is same problem appears on those program? if not, it is just signal desktop that has the problem.