check engine lights, OBD2 code P3458 and P1xx
P3458 normally refers to the intake valve for cylinder 8 on an engine with cylinder deactivation but your Accent doesn’t even have a cylinder 8. My guess is it refers to valve 8 in this case but a guess is all it is. Your best bet is to take it to a Hyundai dealer and let their shop look at it.
I agree with the advice to take it to a shop, but a good local independent mechanic would be just fine for an 18 year old car. No need for a dealership, at least initially.
Normally I’d suggest an independent shop too but with the oddball code it seems like a dealer’s shop would have a better chance of diagnosing the problem.