You can try these two things, surely one of them should be able to help you.
The first one:
- Open your osu! installation folder (right-click the osu! icon on your desktop and select "open file location"
- Find "osu!.db", move it to your desktop.
- Restart osu! and it should process all your maps and the stutter should disappear.
If that helped you, you can just delete the old "osu!.db".
If it doesn't help you, move "osu!.db" back to your osu! folder and try the second solution.
The second:
- Hold down the Shift key on your keyboard.
- While holding Shift, double click the osu! icon on your desktop.
- Continue holding Shift until you see the recovery dialogue prompt.
- From there, click on the "Repair osu!" option
If you don't have a shortcut, make your own desktop shortcut:
- Search "osu!" on your windows task-bar, right-click it and you'll see an option that says "open file location".
- Right-click it again and you'll see "Create shortcut".
- Then just drag it to your desktop and follow the steps above.