Windows 10 Pro PC Performance Troubleshooting

My 1-year-old Dell Windows 10 Pro PC has been exhibiting erratic behavior, with various programs randomly displaying a "Not Responding" message. This happens at unpredictable times, not just during startup or when multiple programs are running.

I've attempted several troubleshooting steps including:
- Disk cleanup and defragmentation
- Updating drivers and software
- Running antivirus and malware scans

Despite these efforts, the issue persists. I'm seeking an experienced IT professional with a strong background in PC troubleshooting, particularly with Windows 10 systems. Your expertise should ideally include diagnosing and resolving software-related issues. Please provide a detailed plan of how you would approach this problem, along with your estimated time for resolution.

I have a 1 year old Dell Windows’s 10 pro PC on which various programs randomly say “Not Responding”

If I restart the PC it works for another few hours then it happens again.It has loads of resources and all O/S and driver updates have been applied. I have ran the hardware diagnostics numerous times and the tests all pass.

I need someone to advise on the way forward and possibly suggest some additional diagnostic software that would actually give me some idea of what is failing or what the problem actually is.