Welcome to iPhoneForums, MythicalMermaid!
Does this happen when a certain app is opened?
If you use Location Services, turn them off. See if that helps.
Try resetting your iPhone. This won't change settings or remove data. Press and hold Home and Power button simultaneously until the Apple logo appears. Let go of both, the iPhone will power up on it's own.
Restore your iDevice using iTunes. Make sure there's a recent backup, so you can restore from it. Here's the description of the procedure:
Use iTunes to restore your iPhone iPad or iPod to factory settings - Apple Support
After restoring, reset again, using the method mentioned above.
If restoring from a backup doesn't help, set it back to factory settings. Again, reset. Add the apps you use, one after the other, and observe your iPhone's behaviour. Maybe one of the apps is causing the crashes. If so, deinstall it.
If all this doesn't help, you'll need to visit an Apple Retail Store so they can take a look at your device.
