wait. if you're having reboots. use a pc/computer with adb commands.
first. you need to have drivers for your mobile phone.
second download and install android sdk. here ->
http://developer.android.com/sdk/index.html
third start cmd (run as administrator)
fourth, type "cd <install location of sdk>/platform-tools"
fifth, "adb logcat > logcat.txt"
run the crash. then press control+ c to stop the logcat, when the system has booted.
copy contents of logcat.txt (located at <install location of sdk>/platform-tools/logcat.txt) to
http://logcat.miuiandroid.com/