Here's the answer:
“mi abuelo siempre iba a correr por la mañana”
Watch a real native speaker say it:
Here's how it sounds in a textbook:
You could also say:
- por la mañana mi abuelo siempre iba a correr
Fun fact: the hundreds of thousands of people learning Spanish with Memrise get this phrase correct 94.75% of the time!