Phlegm and mouth slime (gross)

I've been lurking here for a while and it's helped motivate me to get back to running. I did a lot of running way back in high school but very little as an adult. I checked the FAQ but don't see anything about my particularly gross problem: my mouth gets slimy and my through fills with phlegm. This causes me to spit a lot which seems counter-productive for keeping hydrated. And when it's really bad, like yesterday, I have to stop because I start coughing which has turned into heaving, but not quite barfing. Is this normal? Has anyone else experienced it? Will it go away as my body adjusts to doing exercise again? Any tips for the mouth-slime ridden Redditor?