2013 Yaris (cant remember specifics) stalls then wont start

[Yarisfiend]

My Yaris (26000+ miles) has had the following issue in the past few months:

I will start as usual and the car will stall straight away. When i try to start the car again it just wont start the engine just turns and doesnt do anything for about 10 minutes and then it starts fine. It did the same thing yesterday only everytime i tried to start it again i could hear a hissing noise. The car didnt start for 5 hours.

It was only serviced last September and there were no issues, I have booked it in with Toyota for Saturday but was wondering if anyone had any ideas as to what could be wrong?

Should i prepare myself for a big bill or could this be something that is covered under warrenty?