Connecting to 3G on boot

Hello everyone,
There is a problem with that pppd process. Sometimes it does not connect to 3G interface. If I set stop than disconnect through web interface, it connects again.
If I restart network (/etc/init.d/network restart) it connects internet too.
But on boot it does not connect.
Sometimes pppd process die and start again but it keeps dying.
Sometimes pppd not start again.
Can you help about that?

Varikus possjbke reasins, i.e. low power supply. Or timing probkem when moden poweribg up. Does it always work, in case manual start after boot complete ? Did you try bigger power supply ? Which openwrt-device, modem ?

Hi Mr,
It is ZBT WE826, my adapter is 12V 1A, I will try with more powerful adapter. When I restart network, it always works.