No what you give is absolutely not sufficient. Noone can help you there as long as you don’t provide more insight because it is not a well known problem to occur everywhere.
So there is something specific you did or do to cause this, and that in turn noone but you can know.
You need to find out yourself. Do a strace() [or however that’s called on MacOS, I don’t know] or use a Java profiler to find out what Java does in that state.
Migrate to openHABian on RPi to see if it happens there, too.
Delete the cache.
Setup OH again from scratch.
Enable debugging for rules processing (read the docs about logging and start with log:set debug org.eclipse.smarthome.model.script and extend to org.eclipse.smarthome or org.openhab if that does not give any hints).
If something on your box changes any of the source items or rules files, this results in a lot recompilation, making java CPU jump to 100+%. The aforementioned logging level would create log lines in that case to give a hint).
Maybe you yourself edit files in place or your editor works that way (intermediate saves?).
But please stop writing posts expecting someone to take you by the hand and debug the thing for you.
That won’t happen. Es gibt hier nur Hilfe zur Selbsthilfe, und MacOS benutzt halt kaum jemand.