DVSG3

I have a 01 GS300 with nav and Levinson. I notice when I am driving with the map screen up, the GPS indicator comes on and off. Once in a while, with no GPS signal indicated, I will be quite a ways off track on the map. Is there any way to reset the system once the car is turned on so that the GPS would search for signal and give me a more accurate position? BTW, I have the 2000 ver. 1 maps so I know I need to upgrade. Will work on that this next week, but that shouldn't have anything to do with the signal. I live in the desert with no mentionable trees or obstructions and I have clear skies 360 days a year.