This unofficial Division I list (originally researched in 2021) is based on:
On April 9th, 2022, OU noted in the Texas Tech game recap that their 35-0 record was tied for the best start, but did not list any other teams. ESPN also tweeted the same.
On April 10th, 2022, both OU and the NCAA Softball Twitter account noted that the last 35-0 start was by UCLA in 1999. However, the 2021 media guides for Oregon and UCLA, as well as this 2017 Oregon game recap, showed 35-0 starts in more recent seasons.
If you have any additions or corrections, please contact me.
Since 1980 (does not include Fall seasons)