DNS Problem while working with network

Hello,

I have use my laptop with my office network using LAN connection, In my office all PC has working well on Internet not any problem with Internet Connectivity.
But while i use internet on my Laptop it would be connected just for 15-20 min. after that automatically DNS error occurred on Browser page. after few minutes internet automatically connected and working well for next sometime.
This cycle has repeated 6-7 times in one day.

what can i do to solve problem...