2015 elantra.. engine spins, no compression

Hi.... 2015 elantra.. super weird!
I am mechanically inclined...
last month I went to start my elantra... engine spun very fast as if the starter motor bendex gear was not extending to catch the fly wheel.
I got my daughter to turn it over while I watched.
To my dismay , the crank and serpentine belt and alternator were all turning fine.
Therefore the starter was engaging fine but you could not hear any engine compression gallop.
Boosted it just for something to do... spun like a blender... belts all turning... it was as if there was no compression. Then after many minutes of cranking you could hear the engine compression / gallop starting to build and just as it began to sound like a normal engine.....it started right up! then it stalled.
After another few minutes of the engine start without any compression,,, it started to slowly gallop with engine compresssion , then it started again.. but stalled again.
Unable to restart... callled tow truck. One hour later it started like nothing was the matter.
I took it to the shop anyhow... no codes thrown!
It has been running fine ever since.
This has me weirded out as it will let me down but what on earth can make a car behave as if the cam chain is broken... then slowly build compression and then start!!
I don't think any of the valves hit pistons in all that cranking which is also odd because this is an interference engine
It has to be the VVT.. or vvt solenoid but how on Earth?? what could be going on.
My mechanic is buffaloed.
It has been running fine for a