So... what do you mean by "a service"?  It seems by your statement that the
service was not in address of this problem.  What you describe sounds like a
problem that should first be addressed by a basic tune up.

What kind of "service". An oil change?  If it was truly serviced, they would
have investigated the problem. Could be a lot of things.  Spark plugs,
wires, coils, ignition module.  I'd start with new plugs and wires.  It is
easy to break a wire internally when changing plugs so eliminate that
possibility. (plus, they seem to leak and ground out after five or six
years).