1. Please don't bump your post for at least 24 hours. This isn't a paid repair service - we're all just users like you, some of us know more about cellphones or about one particular phone, but we don't get paid to be here. Some posts don't get answered for hours, some for days. (And some no one here knows the answer to, so they don't get answered, or you're referred to another forum that might have people who have answers for you.)
2. It looks like a weak spring in the power switch, but it could also be a bad connector on the switch assembly (or a carbon path if the phone ever got any moisture in it - even like being left out in a car below freezing all night, then suddenly brought into a warm environment - which causes almost pure water condensation which can take months to start causing problems).
In any event, the phone has to go into a shop for repair - there's nothing you can do without disassembling the phone, which I strongly suggest that you don't do. (If you damage something, and there are signs that you had the phone opened, many shops won't even look at it.)