osCommerce Error - CPU Quota Surge

I'm having trouble with my osCommerce website; an error message pertaining to 'CPU seconds quota reached' keeps popping up. Utilizing your knowledge of osCommerce and error troubleshooting, your task would be to investigate, find the root cause and rectify this issue within the next month. Ideal skills for the job would include deep understanding of osCommerce, PHP, SQL and experience in problem-solving related to CPU usage and efficiency. Your expertise in optimising CPU consumption will be of great value.