Practically speaking, you cannot have too much RAM. If your system is using too much memory it will likely be one of the following:
- The system has insufficient memory to perform the tasks
- Your system has a faulty application or driver consuming too much memory i.e. a memory leak
Observing memory usage in Task Manager when the system is idle should give you a better idea of how much the system is using.
Also, computers that are left asleep (i.e. not shutdown or restarted) frequently can have caching issues and pending updates. Maybe try a restart.