on a Cisco 3550, when i first plug it in it powers up but takes a while for the phone to actually connect/register its extension, it starts the countdown process repeating prov.prequest from 20 down to 0, and at about 9th attempt it will register only sometimes, other times it will keep power cycling
with polycom phones i dont have the problem, only with all snom phones i have tried
its something about when the phone drops the ethernet after receiving power