CPU usage away from normal on Ubuntu 20.04 (Reaching 97%)

I want to ask a question, hope somebody here can answer mine.
I have a Lenovo Thinkpad T40 with Ubuntu 20.04. For the begining, it was normal, but time by time, there is a problem. My CPU usage (one core) is reaching 97% usage. I dont open any heavy apps. I just open my vscode, but the CPU Usage reaching 97%. Please help me.
Thank you for your attention.