How old is the laptop? I had a similar issue awhile back with an HP notebook. The wireless would continuously go out and eventually the whole motherboard did. Never the less, the first place to start would be your wireless router. Just ensure that it is running alright. If that is ok, the laptop may need a new wireless card. If I recall correctly you can order one and replace it pretty easily, as it should be covered by just a panel underneath the laptop.
In the meantime, you can always attempt to update drivers and such for the wireless card.