First things first, the 2011+ radio (can't speak to earlier) will not restart from the beginning of the song list unless you've changed the contents of the USB stick... and then, yes it will.
Second, you hopefully know that you can change the mode-of-play from Song Titles, to Artist, to Album (my preference) or Random. You switch which mode it's in after setting the input to the MP3. Documentation on that is on Page 36 of the
audio manual If all you're looking for is Random, that's about 5 Mode buttons away
Third, if the USB stick has a playlist structure, that will override everything else unless you've selected the ALL mode (instead of PL1 - PL9).
Fourth, if you want pure audio feed from your Clip, you would connect to the aux-audio-in connector in the glove box using a standard headphone connection... but then you have no track-control of the Clip from the motorcycle, but that may be just fine with you.