2010 Chevy Aveo LT over-heating, rumbling start up issue
So not an hour ago I was stopped at a red light when I noticed my thermometer going from normal 1/2H to 3/4H.
I turn on the heater to make it stop heating up as much but the air instead of being hot is actually cold O.O which is something my Aveo has never done before. If I put it full blast hot I get all toasty inside.
When I stop moving it heats up quicker and there are short intervals of hot air and long cold ones. The thermometer doing the same thing, from 1/2H to 3/4H.
***Recent Observations***
When starting the car cold it does a rumble like either the spark didnt catch right, or liquids arent pumping all around well enough. I had to turn the car off and on again for it to 'catch' and be fine. I changed the sparkplugs and the problem died for a good 3 weeks then began again.
I haven't checked my radiator to see if maybe I ran out of anti freeze (what I think is the issue) but this month alone ive filled the tank around 4 times. Is this normal?
**Work done in the 3 past month**
Replaced Thermostat (at dealership)
Oil change
New Battery
New Sparkplugs