At 4%, the palm screen changes USB to the palm logo . I think the phone re-boot .
I can't recover Webos.
Doctor disconnects at 8%
If the webOS Doctor continually disconnects at 8%, then you probably have a corrupted USB drive. This is how you can fix that (note that this will completely and utterly destroy all data on the USB drive).
First put the device into recovery mode, then memboot the device using the installer uImage (extracted from your webOS Doctor jar):
Try running the doctor a few times in Recovery Mode.
Try 10 times. It will be easier to try this, than do the rest.
If you fail, then do the rest
(I'll post easier instructions)
Read this thread. There's a few tips, and easier instructions at the end, should none of the tips work.
Please note it's well possible you do not have a corrupted USB drive, so do not focus on that exclusively.