Phone Does not boot up

Phone details:

Android 4.4.2 Kitkat

512 RAM

1.8 GB usable memory

Phone doesn't boot up

It keeps showing the Model number (like when just powered on) along with a red exclamation mark on the top left corner It doesn't boot up.

However when I keep it dead with battery removed for about 3-4 days it works normally and again meets with this problem after working for a couple of days.

The screen hangs and shows white stripes all over and the phone shut downs and the above mentioned activity continues after I power it on.

Please help