Hello Vicso1208

                              So if your modem SB8200 is booting up automatically, here are some basic trouble shooting steps you can try on,

 While the modem reboot on its own if you find the power light is OFF you can try connecting modem to different power outlet or try using different power cable.

You can also try resetting modem for 30secs without coax cable or you can follow the instruction mentioned on the below link to perform factory reset on the modem. Then monitor the connection fir couple hours if same repeats then we would suggest you to return and get new one from the  place of purchase if it is 15 to 30 days old.

Let us know if this helps.

Thank you for the response. I will try these trouble shooting tips as soon as I can. I actually bought this from eBay and 5he warranty just expired. 

Dear Visco 1208 

Well in SB8200 the modem is able to provide all lights solid when co-axial cable is not connected ,  but at the same time when co-axial cable  is connected all lights on the modem are on and goes off and repeats the same .

In this case please check if the co-axial cable is not damaged . Contact your Internet Service Provider and check on the same .

Let us know if this helps . 

Great idea. I'll have them check them out for me