My 2005 TL has started having a slight front wheel hop that comes and
goes between 40-50 mph. If I lift my foot off the gas it stops
instantly and doesn't come back when I apply power again. I've had it
start up on both right and left front wheels but never both at the
same time. It has become noticible in the last 3-4K miles. I also
never notice it after I've driven more than 10 miles.

The car has 48.5K miles, Michelin tires (original and due to be
replaced before winter sets in) and is not driven hard. The tires
have worn evenly and given good service (but I wouldn't recommend them
to anyone for serious snow driving.)

Is this most likely a wheel balance problem at this point and/or
slight flat spotting that is clearing up as the tires warm?

TIA. Paul C.