IPHONE 6 SCREEN TURN ON AND OFF EVRY 2 min ON LOCKSCREEN plz help

iphone 6 screen turn on and off every 2-3 min on lock screen even if there is not notification.
tried
1. restoring
2. turned off all notification too
but still the isssue is same.

if connect to charger it the same turn ON and off ( but it charging)
but when to connect the phone with PC or Laptop it fine and behaving normally.

ANY HELP HIGLY APPRECIATED.
THANKS