Is there one particular app that is trying to run that is causing the system to crash?
If there is or even if there isn't there are a few things that you could try:
Clear cache is the option you should start with. It will get rid of saved data that allows apps to load a little quicker when you launch them. Clearing it means the app will open a little slower, but your main problem might well be solved.
Clear data will erase all the app's data, including files, settings, and accounts, so don't use this unless you have to.
If the above solutions have failed, you can resort to factory resetting your device. When doing a factory reset, ensure that you have backed-up all of your data beforehand. A factory reset will wipe your device and set it back to factory defaults, taking everything, including any bugs, with it. You can restore your apps and data afterwards easily, as long as you've made a backup.
Hope this is of help, stay safe