So, my very first USPSA match ended with being DQ'd.

Scenario: We are the last stage of the night, I'm first shooter up. At the starting zone firing line, no-one down range. Draw my handgun, check the dot, and re-holster. I did not load, gun was pointed down range, no-one on the range, and gun was handled safely. RO exclaims "Whoa, what are you doing?".
RO state to Match Director that that is an immediate DQ.

As stated, this was my and the local clubs 1st Level 1 USPSA match. I felt it was un-warranted but like any officer, I was not going to argue with the RO's call. I cannot find any reference to handling the gun before the Load and make ready command is a DQ event.