Welcome to Borderlands 3.
It seems a lot of us have similar issues with this game; have a look through this forum and you’ll find several posts about it. Some say it’s the game, some say drivers, some say Denuvo, some say Unreal engine.
I have had this issue for months, and have spent countless hours trying to find a solution, even going so far as to switch from Windows 7 to 10, switching to a ssd for both the OS and game, and buying a new video card. Nothing has helped. Can keep a constant framerate of 90, but still stutters when I pass a machine, etc.
So while I can’t help you; know you’re not alone!
I should also note that the new Radeon drivers (March 5) have as a known issue:
“Some games may exhibit stutter intermittently during gameplay on Radeon RX 5000 series graphics products”