Photos app is installed as default on Windows 10. You can use this app to trim videos.
Open video in Windows 10 with Photos app. Usually it is the default app to open videos, so you can just double-click it.
Click on “Edit” icon (pencil icon) on the bottom right hand side. Select “Trim”.
Drag the start and beginning of video to adjust it.
Click on “Save a copy” button on the top right hand side.
Select a new name for the video and save it.