The marching glute bridge is a great way to prepare your glute muscles for the more advanced single-leg glute bridge and also fire up your core and hip flexors. Take this one nice and slow; don't try to rush through the reps.
Lie on your back with your knees bent, feet flat on the floor, and hands by your sides. Engage your core, and raise your hips up to the ceiling so your body forms a straight diagonal from shoulders to knees.
Lift your right leg off the floor, keeping it bent at a 90-degree angle, pausing when your shin is parallel to the floor.
Slowly lower your right foot to the floor, then repeat on the opposite side. Try not to tilt or drop your hips or arch your back.