You don't need the power button to restart your Android. If yours is broken or you simply want options, here are two.

Android devices will now automatically restart after 3 days of inactivity for security. After a restart, the phone enters a security mode where data is inaccessible unless you enter the unlock pattern ...

The latest Google Play services update includes a new security feature for Android phones. The feature auto-reboots devices if they remain locked for three consecutive days. This new inactivity reboot ...