Hi,
I know random drops in service can be frustrating. Many things can cause intermittent drops in service. In some cases, restarting the modem can help, but if it does not, then we will need to look at other possible causes. First, I recommend checking the coax cable that leads from the modem to the wall to make sure that both ends are tight and secure. The next this would be to narrow down what is causing this. Try bypassing the wifi router if possible and connect your computer directly to the modem with an Ethernet cable to see if you continue to have the problem. This will let us know if wireless interference may be the cause. If the problem continues, then a tech visit may be necessary to get htis fixed.
Greg