I leave my house this morning and the heat is working just fine. I pull into the parking garage and sit at idle for a bit and notice there is no longer hot air blowing, its all cold. I read on a a general car message board that it could be low coolant. I've also read that if I touch both hoses and one is cold then its a clogging issue. Are these to two basic things I should start with before I take it to the mechanic?

Is there any coolant leaking into the the interior around the the front floors at all? Check the hoses first. If those are good, you may have a bad heater core.

start with checking the hose, check your coolant levels, and (the harder part) check to make sure your temperature vent door is not stuck.

another thing that comes to mind - heater bypass valve on the passenger side; this may be stuck in "a/c mode" and not allowing coolant to circulate through the heater core

Alright, so I get back into my car and leave the parking garage and the heat works. Same thing this morning, start my car, heat works on my way to work but when I pull into the parking garage it turns cold. The only thing that is constant with both days is the engine temperature is running a little hot when the heat turns into cold air. Any thoughts on that? Thanks!

After reading that, I think it's this:

Or a clogging heater core.

my old S10 did the same thing.....I had to back flush the heater core....fixed the problem...tons of junk came out of it...