Physically, singing is a kind of athleticism, and will benefit from a program of exercises that works on flexibility, strength, registration, and vowel quality in daily practice. If you have had a break from singing and want to get back into it, it is important to start practicing easily, and gradually increase difficulty and duration.
Use exercises that emphasize movement over resonance. Keep them simple. Warm up registers separately and bring them together gently, gradually increasing volume if it feels good. Work with a voice teacher who understands how voices work and how to train them, not someone who only teaches repertoire and style.
If you are a singer who hasn’t done exercises, only repertoire, this recovery period will take longer and may not even happen. It is frequently the case that people come to me after a long break because they have never had to strategically practice exercises from simple to difficult, and their old repertoire is presently impossible. Getting back to performance shape is a matter of learning how to train. Once you have successfully worked through coming back from a break, you can take more of the responsibility yourself and rely a little less on a teacher to “fix you”. It is still important to have lessons, but realize that the good teacher will show you things to do and not just do things to you. Magical thinking will not make the recovery faster. It takes good guidance, intelligent practice, and time.