My personal favourite, a good knee stretch really helps my tight hip flexors.

“The knee hug will stretch your lower back, hips, hamstrings and your inner and outer thighs,” agrees David Wiener, training and nutrition specialist at Freeletics. “This stretch can be performed either standing up or lying down. All you will need is a flat surface and possibly something to help hold your balance, such as a wall, countertop or chair back.

Lying on your back, bring both knees towards your chest and hold
Let go slightly and move your legs in a circle to help mobilise your lower back before getting back up

No time to stretch? These are the 5 moves you need to make time for, according to PTs