Usually tends to indicate a line issue. 

did you check all the coax connections?

Or check with the isp?

I connections are ok. but still i experience this issue at morning time. Thanks

Hello olusola09

As you also mentioned co-axial cable and lines connections are fine .

 This is a gateway device , which is a combination of modem and router , we need to check the values of downstream power/snr and upstream power values which is the cable signal levels 

To check on it follow the link below:

http://arris.force.com/consumers/articles/General_FAQs/SBG7600AC2-Cable-Signal-Levels

Do screen share the values so, we can understand the issue better .