I strongly suggest opening a case with our support team.
There must be a reason for your CPU to spike and support can help you identify the cause.
I do not suggest trying to configure the heap memory at all.
what is the version from your Tableau Server?
Normally, the process that use lot of memory is vizqlserver.exe
How is your configurations from Tableau Server?
Thanks for your reply.I already contacted them.Will Update this issue if they find a solution.