What I mean is, are you noticing any deterioration in performance or any other unwanted effects?
RAM usage 'may' be a sign of something unusual happening, but there is a bit of a misnomer about excessive RAM usage. We seem to believe that if the system is using too much RAM there must be something wrong. I'm not entirely sure why that should be though because RAM is there to be used, and if it isn't then it is being underused. Your system has 4GB of RAM so 4GB is available to be used.
That said, I would run some anti-malware scans with Malwarebytes' Anti-malware and SUPERAntiSpyware. Install both, run and update them, then run separate full scans with each. There may be malware infections and it is always good to have second opinions with these scanners.
You don't say what OS you have and that may be relevant. For example with XP a system running with more than, say, 35 to 40 processes might have been considered busy, but both Vita and Windows 7 normally have more processes running. Also, with Vista and Win 7, the Task Manager Processes tab has an option at the bottom to "Show processes for all users". Click that and you may see even more processes running.
How often do you shut down this system? I've seen machines that are left on continuously and in those the RAM is never emptied and released. In such a case a reboot might work wonders.
Without knowing more about individual systems it is difficult to be precise, but 30% RAM usage is not a particularly worry.
Mark