It is most likely an issue with either something pointing to a network server that does not exist (30 second timeout which can block other things) or with a third-party component like a shell extension (e.g. Dropbox or another cloud sync tool) or antivirus. This guide has suggestions on tracking it down:
If you wish, you can also send us process snapshots made while the problem is happening, which can often reveal the cause with issues like this: