You can use ffmpeg, and you currently have a choice of four video filters that can blur:
unsharp. These filters have timeline support, so you can blur just a certain duration or durations if desired.
ffmpeg -i input.avi -vf "boxblur=enable='between(t,22,113)',boxblur=enable='between(t,(60*4)+35,286)" -codec:a copy output.avi
You can enter seconds or have it calculate seconds for you as shown in the example.
Expression evaluation is not my best area. You may find a method to declare the filter just once.
Note that, since you only want to modify the video, the audio can be copied from the input to the output without re-encoding. This is faster than re-encoding and will preserve the quality.
If you have
ffplay you can get a preview instead of encoding, watching, re-encoding...
ffplay -i input -vf smartblur
Most Windows users will simply want to visit Zeranoe FFmpeg Windows builds, but of course you can always compile ffmpeg too.