All the cars I've had or rented that did this, it's only normal for them to make the trip once. If your's is doing it multiple times I would get it looked at next time you get the chance. If the car is running fine it may be nothing but it could be a sign that your instrument cluster is getting ready to fail (my parents van loses the guages pretty regularly).

Hey if the gauge does fail and you get pulled over you could always tell the cop "officer my spedo said I wasn't going over 55mph"