Most things are secured pretty good in a PC case here are some things I would double check.
1. CPU heatsink - Make sure it still securely fastened. Rock it gently, making sure non of the 4 corners give. This may vary depending on the cooler you PC uses.
2. Hard Disk Drives - Most hard drives are protected against shock especially while off. Hopefully your HDD support S.M.A.R.T. The article I'll link will show you how to check SMART status to make sure you HDD are ok.http://www.howtogeek.com/134735/how-to-see-if-your-hard-drive-is-dying/
3. GPU - If you have an add in GPU, especially one that is not screwed to the case give it a gentle push toward the mobo to make sure it's still in.