Well, if you are just starting out doing neck bridges, try doing front neck bridges and back neck bridges on the same day ... then wait and see how your neck feels the next day. If you are new to this, then honestly, regardless of if you are sore or not, I'd let your neck have a couple of days rest ... then after those 2 -3 days, if your neck feels ok and has normal flexibility and rotation, go at it again. Make sure you pace yourself rather than just diving in headfirst (haha, a funny) and not allowing your neck enough time to recuperate and risking injury.
Pay attention to how your neck feels. If your neck is real stiff and you have a cramp or something, lay off and let it rest until your neck feels normal again. Now, if you just have some soreness in the muscle area, that's obviously normal, so just give it a day or two.
Eventually, the stronger you neck gets and as it adapts, you'll be able to do neck bridges more and more frequently, even to the point of doing them every day if you'd like. Your neck will start getting less and less sore as it adapts/gets stronger. I do neck bridges everyday, but I don't do the same one's every day, usually. I'll do something like:
Mon - Front neck bridges and side neck bridges (where I tilt from side to side rotating on my forehead and hold it for a while on each side)
Tues - Back neck bridges and side neck bridges (same as above side neck bridges, except I am rotating/tilting on the back of my head rather than the front)
and I usually just keep alternating these all throughout each week. Note that I've been doing neck bridges regularly for 3 - 4 months ... so eventually you'll be able to work up to something like this. be careful
