Originally Posted by Juke16
One thing that may be an issue is if there's some solder left on the tip. Have you tried to leave it on for a while and see if it emits heat of any kind? If it's emitting heat AND there appears to be residue on the tip, wait for it to heat up the residual solder and try to wipe it off on a piece of metal.
Actually, the opposite is true, you NEED to tin the tip with a big blob of solder before turning it off, otherwise oxygen will cause the tip to corrode and it'll pit, or at a minor level, become glazed to the point the tip won't melt solder anymore, and needs to be scrubbed down to bare metal then tinned again to make it work right.
And having the tip go funky won't cause the soldering iron to turn on, that's an electrical issue.