Semi loud vibrating sound when car is idle, does this mean a tune up or timing belt problem? 1996 Camry

Not sure of the mileage requirement for a timing belt change, but the problem could be multiple things, many of which a tune up would find & repair:
Plugs & Plug wires
fuel filter
air filter
Any of the emissions systems

If fuel filter or air filter are due for replacement, can start there relatively cheap.

How many miles total on vehicle? How many miles since any major work or tuneup? Has timing belt ever been changed & if so, when?

Does sound go away totally when driving? Try driving along side a wall, where the sound can bounce back at you, with windows open, radio & A/C off, to see if you hear anything. Wondering about exhaust system leaks.

Need more information to determine more likely causes.

I have a 1996 hyundai elm with 129300 miles on it.it vibration at 40 mph.could this bbe that i need a tune up

Sounds like a bad motor mount not keeping the engine stable