i dont know why, but it never happened on my old pc. the new one is 2 months old. it has ssd (where the windows 8 is) and 8gb ram.
plus, i have set the paging file to 2048 to 12248 mb as
so the thing is that almost twice a day i must restart the pc because the ram gets to 97-99% of usage and then it gets stuck.
maybe its a cashing problem?
please help. thanks in advance.

If you have "Channels" on try turning them off. Settings then forth from the top channels, click, first thing lets you turn it on and off. Also minimize Tixati when you are not looking at it. That is true for any program, showing the interface requires more resources.

if your using windows, try installing taskinfo from iarsn

It monitors multiple factors for each process. It has several columns for RAM related usage. It also has a graph for overall RAM use which if configured for max time will show gradual upward slopes which sometimes indicate memory leaks.