Did you recently upgrade to El Cap or run another Apple system update?
There are no guarantees CS5 will run on El Cap. It's hit or miss at best and getting worse with each Apple update.
Unfortunately Adobe stopped supporting CS5 years ago.
If you still have it as an option, you can try uninstalling and reinstalling the app or upgrading your software.
Any error message? Does the program open completely? Have you emptied the InDesign Recovery folder so it won't crash trying to auto-recover corrupt data?
If you have a crash report, put it on Pastebin.com and give us a link to it.