Since the beggining of this season i have also been hit with the New transfer market in one of my teams, since then i have studying it and at least on this server i now know how to find 5* players.
During the day you Will only see 3 and 4* players, and even those Will have diferences in auction time, the 3* players Will always have more time that the 4* players.
For what i have seen 3* often starts with 1h or a bit more to the end, 4* Will start with 40 to 50 minutes to the end, but this can be diferent depending on the server.
In my server all the 5* available Will only appear one time in every hour! maximum time of auction 25 minutes.
In my server that happen between the 5th and the 20th minute of every hour, for exemple 8:05, 9:10, etc not the same exact minute in every hour.
To see them all you need to keep refreshing the page, until you cant see anyone New appear, at least on iPad i have to do it this way.
Today auction at 6:05 am
After refresh
Today at 7:10
Today 8:10
After refresh around 8:20 If you compare you Will see that are some diferent players
I cant confirm this Will work in all server, and for how long, but you dont lose nothing trying to discover your server lucky hour!