Windows have never cleaned up the %temp% folder properly on shutdown or reboots. You can always manually delete everything in the folder. The only exception is if you allowed something to install in that folder. Many Anti-Virus products scan that folder heavily so the more files that build up the more resources taken up defending against those files.
I'd delete the files that it will allow you to delete then run a disk cleanup including a system cleanup of patches to windows, you can get to it through windows explorer right click on the C drive and click on Properties, then click on disk cleanup. Once done reboot the PC but will may have to wait 30 min to an hour if any updates were hung up.
If you see Trusted Installer in Task Manager running with high memory usage say 250k or higher you should definitely consider running the Disk cleanup!
And yes never install an update right away, always set windows updates to allow you to install them, check the update wait a week then search on the update to see if it created any issues.