When I turn on either my a/c or my heater I get a small out of the vents for about 5-10 minutes. Best I can describe is that it is a sweet smell.

any ideas what this could be?

 

Sounds like your heater core is leaking. I would start with pressure testing your cooling system.If your core is leaking, it is a labor intensive job involving disassembly of the dash and possible evacuation of your a/c system.