Nothing particular to the Radisson Shuttle. The hotel shuttles generally run 20-30 minutes, and it takes about that long for one to make the loop around the arrivals level at LAX.
Since you won't have any bags, you will have a much quicker time on your flight departing LAX. Are you flying out of TBIT or Terminal 8? I forgot how UA does their int'l flights. Either way, plan on getting to the terminal 2 hrs ahead of flight time.