Most of the time those issues have nothing to do with the modem. If you are having issues, start at the beginning and explain what is going on and what you tried already and what your computer setup is like with the network.
You also need to list what connection you want it for, cable and DSL have different types of modems.
If you are just looking for a modem and don't have issues you are trying to fix, the Motorola SURFboard DOCSIS 3 is a standard and good model for cable connections.