Well there is a known issue with bootloops after disabling the Google App.
If you didn’t disable that App, then it sounds like an issue with the battery (not strong enough to finish the app optimization process).
Try the battery reset as described in the batteryguide.
If that doesn’t help - I’d get back to the idea that it’s a software issue and you’ll probably need to do a dic:hardreset, which erases your data! To do that check out how to get to dic:recoverymode, as the procedure has changed slightly on Marshmallow.