SLK Bulb failure warning problem

Dear Sir:
Greeting and good days ! Here's a problem
with my SLK230K (1997) :
The bulb failure warning (yellow) light
turned on suddenly during I driving on free
way , and I stop by side (engine still on)
to check all external lights (including head
lights , braking lights , turning light and
others) , all are fine ; And when I restart
engine , the warning light turned off , but
it turn on suddenly after driving a while .
Please give me a favor to reply me ASAP
, thanks in advance !

-YC-

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YCChou