Is there any reason not to heat up the oats in the morning, if I prefer to eat them warm?
You can definitely heat them up in the morning if you want to.
I like my warm too so I let them sit overnight in my small pan and then just do a quick heat up to warm up. It's a favorite breakfast of mine making them savory - turmeric, salt, black pepper - and if there's time in the am a soft boiled egg on top and some greens... Mmmm
I absolutely prefer them warm! I make a pot at the beginning of the week. On the first morning, I spoon what I want into a bowl, cover with waxed paper and microwave for a minute or two, then add whatever I am going to add (fruit, nuts, jam, milk, etc.). The rest goes into a sealed container which I keep in the fridge and dip into over the next few days, until it's time to start again. Yum!
No reason! Overnight slow cooker oats might be a good option - warm, easy and delicious!