I am just starting and am feeling dizzy already now I know why, that suggestion of resting for 20minutes seems perfect, because working so hard without rest, wear off energy in our body tissues, ligaments, tendons and leave us with so much stress shown on our faces and body especially for new members like me, so I make adjustments until I find a perfect solution that will propel me to do push up better everyday.
Beginners who feel dizzy when they start and immediately need to rest, even if only for a moment, are still considered normal. Because beginners really need to practice on their own to get used to any pressure one day, but every beginner also needs to get a little motivation formula so they can have a little encouragement within themselves to keep trying without taking much rest. Just think of it as a good start for you to start so that over time you won't get tired easily when you haven't finished something on time.