Same problem
Something similar happened to me. Visited a friend about 15 miles way every thing was working fine, stayed for a brew and came out 40 minutes later, started the bike, sat nav not working, stopped, switched the bike off and on again still nothing, Took the sat nav out of the mount tried to switch it on manually, no joy. Refitted it to the bike and rode home. Tried again when I got back but it just would not power up.
So booked it into my local dealer (still under warranty). Two days later set off to the dealers still no sat nav, halfway there it came on.
Because it was working when I got there the guys in the workshop could find no fault. When I got home I did update it to the latest maps and I think some additional software was installed as well.
It's been working about a month now, though not many miles because of bad weather here.
We are due to go to Spain and Portugal in June for 3 weeks and I must admit I'm a little worried after hearing other people are having the same problem.