I Live In Massachusetts. A Very Healthy 46 Year Old

I live in Massachusetts. a very healthy 46 year old female, I take no medications. Lately while walking, I have been doing 5-8 miles daily outdoors, I have had an extremely difficult time swallowing. I am a nose breather and dont feel like I am struggling for oxygen, but once I get my heart rate up I tend to breathe in thru my nose, exhale thru my mouth. It has been in the 40s, temperature wise. Its almost scary when I have the need to swallow. As if I would swallow my tongue!! Inside I do not experience this. Any suggestions to keep this from occuring