Inspired by this question, koedem proved that, from the starting position, White's legal move amount can be decreased sequentially from 20 to 0 in 20 moves. However, doing so required some checks. I wondered if doing so was possible without check.
In experimenting, I found a method to up the starting position to reduce to five legal moves without utilizing check.
[FEN ""] 1. a3 a6 2. f3 a5 3. h3 b6 4. b4 a4 5. b5 e5 6. g3 Bb4 7. g4 g5 8. Bg2 Bc3 9. Bf1 Qf6 10. f4 Qxf4 11. Rh2 Qxh2 12. h4 Qxg1 13. h5 d6 14. h6 Bxg4 15. e4 Bxd1
But I highly doubt that it is possible from the normal starting position (but is may be possible, I just think it unlikely; if so, it still counts as a valid answer). Is it possible in a Chess 960 position?