Welcome to Android Central! That doesn't sound good.:-\ If it has a removable battery, see what happens if you pull the battery and then reinsert it. If the battery is nonremovable, then press and hold Power for about 20 seconds to force a shutdown (Power and Vol Down if it's a Samsung phone). Then wait a few seconds, and try to power on again. If the same thing happens, it's probably a major hardware fault, and you'll have to bring it to a repair shop (or contact the manufacturer, if it's still under warranty).