The processor speed and core rate will increase or decrease automatically as the system needs it. Based on your description, my best recommendation for you is to run the Intel® Processor Diagnostic Tool. This software will test and diagnose every internal component in the processor and will generate a result. You can get the software at the following link:
Intel® PDT 64 bit:
Intel® PDT 32 bit:
Another good recommendation is to contact the computer manufacturer so they can help you with troubleshooting steps ir a possible replacement.