my phone was doing the same thing and i found that the battery connectors were pushed in because i changed the sim card between phones very often...what i did was to put some thick double sided tape at one end so the battery fits more tightly....it was working fine but i decided to take it to the nokia care center and they check it (without the tape of course) and they gave a new phone, actually it was a refurbished unit but i think it had been reset bcause there was 0 usage time

same prob here, dont know if there is updated firmware to fix though

Yeah,.. i think u should bring it back to Nokia Care or something to clarify the problem of your fone....

I think some unholy forces are at work...

also try getting one of those rubbers that have a rough side and a soft side (that are blue and white) and rub it on your battery connections

i think that u must buy a new battries or go to nokia protec and let them check it !!!!!

I have a problem with my 3650... Sometimes it turn off by itself... even though the phone is fully charged or still have power. I dunno why. I didn't press the power button at all! For example 1 day, I left it on the desk in my room and when i came back like an hour. I found out that my phone is off. I have to turned it back on again. It happen like this a few times. 1 of my friend have exprienced this problem with this 3650 too.
Have anyone ever expericed with that? Does any one know what caused it to turn off by itself?