DELL INSPIRON 15R 5537

Hi, I purchased Dell inspiron 15R 5537 about a month ago and since yesterday I am experiencing a problem. at times there are 11 dull spots at equal horizontal distances starting from the start menu icon towards the end of the task bar and then it becomes ok by itself. Whereas the rest of the screen is perfectly fine. The problem started initially when the screen went dim on its own leaving dull spots, I restarted my laptop 2-3 times then, initially the screen remained ok and then the screen went dim suddenly every time. After a while the screen became ok . Today when I switched on my laptop, the spots/shadows remained in line on the dell startup till the loading of the windows. The problem didn't go even after restarting it 2-3 times. Then I ran the startup diagnostics and during the diagnostics the spots were there but they disappeared during the test. How to resolve this problem permanently, I am a bit worried.