Need to restart CM1200 on a regular base to get 100% Internet speed both Up and down

> [...] I see my internet drops to 10% speed - 20/30 MPS. [...]

   "see" how, exactly?  Using a device with a wired or wireless
connection?

> 6. Have latest updates

> [...] (R9000)
> Firmware V1.0.5.18

   I see "V1.0.5.24".

   Visit http://netgear.com/support , put in your model number, and look
for Downloads.  (For older versions, under Firmware and Software
Downloads, look for "View Previous Versions".)  Find the kit(s).
Download the kit(s) you want.  Read the "Release Notes" file for
instructions.  (In the User Manual, look for "firmware", and,
especially, for a topic like "Manually Upload Firmware to the Router".)

   Failing a helpful User Manual:

      https://kb.netgear.com/23960

> Need to restart CM1200 [...]

   How did you decide on the modem, rather than the router, as the
source of the trouble?  When the problem occurs, I'd yank the router,
connect a computer directly to the modem, and see if the problem
remains.

   I might also restart the router instead of the modem, and see if that
helps.

> [...] This does not always work [...]

   Another reason to doubt your current blame assignment.  A Web/forum
search for your router model might find some complaints about it and its
speed.