Does your PC sit in open air environment............meaning the fan that keeps the PC internals cool, is not blocked by anything like books, or wall or anything that does not let the warm air exit easily.
If the PC warms up, then CPU usage is falsely raised and so is memory. May be the vent of the fan is clogged in dust or something. Open the PC and do a little dust cleaning and especially in the fan area and vent.
High CPU Usage May Be Caused By...
Out-of-date drivers (Run DriverUpdate to automatically update or manually update them)
Running too many applications at once
Insufficient virtual memory (How to Fix Virtual Memory Issues)
Overheating/Poor ventilation
Virus/Malware infections
If the PC warms up, then CPU usage is falsely raised and so is memory. May be the vent of the fan is clogged in dust or something. Open the PC and do a little dust cleaning and especially in the fan area and vent.

High CPU Usage May Be Caused By...
Out-of-date drivers (Run DriverUpdate to automatically update or manually update them)
Running too many applications at once
Insufficient virtual memory (How to Fix Virtual Memory Issues)
Overheating/Poor ventilation
Virus/Malware infections