I just bought a 2012 Hyundai Elantra Touring with 112,000km. I had a mechanic look at it before I bought and there were no major problems, and none flagged with the engine.

Every time I start the car I get a loud squealing noise from the engine just for the second I hold the key in the "start" position. Once I release the key and it moves back to the "on" position the noise stops.

I read that squealing on starting can be a belt when the engine starts cold and it goes away once it warms up. But this seems different because I get the noise when I start hot or cold and it only lasts until I release the key, and doesn't continue until it warms up.

Any ideas what might be causing it? And if it's anything to worry about?

 

Without actually hearing the engine start up, would say that the belts are probably squealing.
You could take the belts off and start the engine to see if it has the noise then turn the engine off promptly
That would give you a definite answer to whether it is the belts or not