[WIN7] Network drive not consistently connecting on startup

I've recently set up 4 PC's to share a Synology network drive in a small office. But there's a big problem, in that 75% of the time, when starting up, the network drive is reported as not connected. But a few seconds later, everything connects. However, all user files including links, desktop items etc are on the network drive so don't come up. A few seconds later, or a refresh and the desktop items do, but not the taskbar shortcuts. This is on 4x W7 Pro PC's with SSD's running on WiFi. It's almost as if the PC starts on the SSD's too fast before the wifi connects, reports the lack of network drive, then the wifi connects and it's back, but by then shortcuts are lost etc. Can anyone advise on help, as this is a really big issue each time the PC's start up. Thanks.