Do a mold test in your house and get your vents cleaned. Vacuum more often and change your clothes when coming in from outside. Wash sheets more frequently.

My first guess would be allergies. Indoor allergies like dust mites and what not can come into play. Personally for me using Flonase daily and using a neti pot (or similar saline wash) daily has really helped to reduce night time congestion. I also find when your turn your house from A/C to heat, the blowing of the heat into our room stirs up a lot of dust - we use to have one vent right below my pillow - once I moved the bed the night time dry/tickle cough was reduced.

I had a cold about three months ago and even though I’m better during the day, I get congested over night every night and wake up with a cough. It gets better during the day and then worse again over night. This has been happening for months. Any ideas? I’m 50 and otherwise healthy.