Bike fit / correct riding position

I am predominately a runner, but I do still ride from time to time. I'm actually hoping to increase my mileage, but I find that after 10-15 mins of hard effort the hamstring in my right leg hurts a lot.

Does it sound like running has caused an imbalance in the muscles in my legs/lower back/glutes?

Is it a case of trying some shallow squats to help my Glutes?

I get this. I feel that cycling keeps the hamstrings stretched more than running. Which continually stretches and relaxs them to a higher degree.

This means going for a run after a lot of cycling actually feel Nice, as it seems to loosen everything up. While going for a ride after a lot of running does the opposite.

I've been stretching and taking magnesium. As it eventually causes cramp. I also run less when a cycle event approches. Not much of an answer sorry.

I'd check sleeveless sites.