Simple program for trimming video
Depending on the format you have your video, one option is VirtualDub2.
It is a free linear editor, but it is good to trim a video without recompression.
Go to the Video Menu and choose direct stream copy. Do the same with the audio.
You need to do it one by one. Make a backup first. Open the video, cut the end of it first so you do not need to recalculate the timing and then cut the start of it, and save with a different name.
If you want to automate it and you are fine with command lines, try FFmpeg.
https://www.google.com/search?q=ffmpeg+batch+trim+video
If you need to do a bit more, like adding fade in and out, and control a bit more the trimming, you can use a free nonlinear editor, but most of them will recompress the video. Davinci Resolve, Hit Film Express, Open Shot for example.