iPod

i have a MX5 venture edition 63 plate

 audio unit with tom tom

I’m  told to plug ipods into usb and conect the RCA Composit leads red white yellow which i have done while using a ipod classic ipod, touch gen 4 and 6, all work great fully  accessed through stearing wheel controls  except the audio unit keeps disconnecting the ipods after 5 miniutes then scanning which then connects only to disconnect again in a couple of minutes then disconnect scan reconnect . can anyone shed some light on this