BB reboots periodically

[The+Arks]

Hi, my BB was upgraded from 500 to 900 as I had to switch from Sky Q to stream. Ever since my BB reboots every so often, most days. What could be the cause. Do I need a new router as I'm on the black oblong one still so does the 900 need a newer model? Would surge protector work if it could be the power to the router. Tearing my hair out with Sky. 

any help is much appreciated 

 

[peter-marlow+1966]

I have sky wifi max  with  my gigafast broadband and have had  no problems 

I switched  nearly  3 years  ago