@ggodoree Verify which version of Java ImageJ is actually using by clicking the status bar. And try using the Stack Dump command (shift + ) after the program freezes, to see information about what is happening.
More information is needed to diagnose the issue, but the "Debugging JVM hangs" guide linked above gives you the tools you need to get that information.
I tried opening image J by using via terminal. I typed open -a Fiji and the program was opened. However, when I type ctrl + shift + \ during freeze (with active window on terminal), nothing happens? I don't see any log shown on terminal window.
Also, the other thing noticed is that once the program freeze, and if i wait for 10 minutes, the program responds... which is still not normal but takes long long time to process...