It needs more than 4 to go ready to navigate. +- 7 with data the first time.
Do the lines turn blue ?
When the lines turn from hollow to blue it means that it has captured data from satellite.
Try to go to simulation mode and set location to your house. Then put nuvi in power saver mode and then wake it up again.
I do this trick when I travel to UK and it seems to help a bit.
You must set display timeout to never !