My computer and network

Sometimes if I am using the network, my computer is so slow, it won't keep up with my typing. The keyboard is slow and the mouse is very difficult. If I unplug from the network and go wireless, I don't have the issues. I also have some problems just plugging in my laptop in the morning, sometimes it comes up sometimes it doesn't. If it doesn't, I have to open the laptop and then it shows on the monitor?? Any ideas? Laptop: MacBook Air 1.8GHz 4GB RAM, 120GB hard drive, running 10.5.7 Display: Apple LED Cinema Display