This “memory leak” you describe may be normal behavior with all modern OS.
All modern OS nowadays is of the philosophy that unused RAM is wasted RAM, so if your system is busy it will naturally use more of your RAM all the time.
If you are continuously at your keyboard, when your system reaches the maximum available, it will discard data that’s not likely going to be used again to make it available for new tasks, but if you’ve been sleeping all night, your system might have been gradually filling up with no indication that you intend to run new tasks until you start typing… And then depending on what you are doing may have some difficulties estimating how much RAM needs to be freed up for your new tasks so might pause for a while.
There are ways to identify unintentional and actual memory leaks, they’re usually associated with programs you’re running.
If you’re sleeping while your machine is at work at night for long periods of time, verify you’re not experiencing pauses or freezing during the day or your normal activities. If the problem is too onerous in the morning, try “waking up” your machine by scheduling something to happen before you sit at your keyboard.
The machine is left on overnight, for example, when I leave my desktop at night I am using for example 3GB of RAM, when I come back to it in the morning I’m using 3GB of RAM. The OP is for example using 3GB of RAM, when they come back in the morning it is using 16GB of RAM and unresponsive. Ergo NOT NORMAL Behavior, a memory leak for sure in what ever applications are running…
When you’re ready to goto bed each night, shut down a different one of the big apps first. Repeat each day until the leak is absent when you get back to work. I’d start with LOC or VNC Viewer. I don’t imagine you’re doing much calculating or viewing while asleep.
Lots of suggestions here. I will add one.
Are you having these same applications active during the day? Then check e.g. every hour how much memory each one uses. You may be able to see which of them grows. Same of course during he night, but I will not suggest to wake up every hour :P.