Thank you all for your thoughtful comments.
I have thought that the water temperature might be a concern. When the bed was set up previously, the flannel pad used between the sheets and bed was insufficient to keep me from sweating because of a loss of air circulation under me. To solve this, I added an afghan and a sleeping bag to allow for more air circulation between me and the mattress.
During the nights where I had my issues, only the pad was in use between the sheets and the mattress. I'm going to try adding those extra layers tonight and see what happens. Worst case is that I have more laundry to do in the morning but that is starting to be routine so no big deal.
Because the occurrence only happens in one bed, I'm going to hold back on the doctors for now. I'm about to take a trip to do a little job hunting and stay with family, resulting in a complete change of beds again. Should I continue to have a problem, I will consult a doctor.
If it comes to consulting a medical professional, what questions should I ask before I go (so I can be more knowledgeable about my case) and what questions should I ask when I am being seen by the doctor?