Just curious

I just bought a new 04 F-150. When you start it up all the gage needles bounce for a couple of secs. It just started yesterday after 2 weeks of ownership. Dealer appt. on friday, but I'm just curious if this has happened to anyone else and what it might be and what the problem was. Anyone know? It's an XL W/4.6 Triton

Adding info: When starting it acts as tho the battery is low but when it catches All the gage needles vribrate a few seconds then smooth out. If I shut it off then restart it every thing is normal. It only happens when it sits for a while