Precision Tower 3620: M.2 SSD questions

I have a new Precision Tower 3620 Desktop that I've had for a year and have used it about a dozen times since. As far back as I can remember, the performance has never been great. There continues to be a couple second delays opening even the simplest of windows files.I'v run diagnostics and ensured the system drivers were updated and still has made no progress in its performance. Any recommendations would be helpful.