hopefully the bolts connecting engine and transmission are not loose.
It could be the starter motor not retracting fast enough.
Get your alternator checked.
Check your belt tension.
The whirr noise on start up which just just a few seconds is from the fuel system pressurizing due to a faulty fuel system check valve. After the car has sat overnight, turn the key to the ON position so that the fuel pump runs, but don't try to start the car. Let it run for few seconds, they try to start it. If it starts without the noise, it means that check valve in the fuel system in malfuntioning and allowing the fuel to drain out of the lines when the engine is not running.
the fix is to replace your timing cover with a 2013 cover
Looking for a Used Elantra in your area?
CarGurus has 51,593 nationwide Elantra listings starting at $950.
Search Hyundai Elantra Questions
Hyundai Elantra Experts