Start on at
Definition 1 of 2
Pro Tip 1/3Task-Oriented
Use 'start on at' when discussing the specific time to begin a work-related activity. 
Let's start on the report at 10 am sharp.
Pro Tip 2/3Scheduled Events
In event planning, 'start on at' sets the exact time for the beginning of an event. 
The conference will start on at 3 pm.
Pro Tip 3/3Sequential Actions
Use when sequencing tasks; indicates the next task and its start time. 
Finish the current job, then start on the next at noon.