AW: There are multiple issues that may lead to such problems. Please check the place and position of your GPS-receiver which is usually behind the windscreen on the dashboard. The fixation of the GPS-receiver may have suffered due to vibrations and bumpy roads. Another reason can be your park position or parking time (extended period, metal constructions or concrete walls may cause interferences such as reflections and shield your receiver from GPS satellites).
Please also take note that in case if you need precisely route guidance, you should check the GPS signal before you start to drive around and before you enter an address for route guidance, otherwise the system may need extended time to do the so called sat-fix, which is best and fastest if you and the car has clear view to the sky.