This morning he was the same. E picked him up and placed him in our bed while I warm up his milk. When he saw his milk bottle, he pushed himself up on all fours and moved his body as if trying to crawl towards his bottle.
After a few unsuccessful attempts to inch forward, he flipped over and with arms outstretched, started to make the "milk" sign with both hands while making eye contact with me. I was so overjoyed, thought it could be just a coincidence, so picked him up and moved towards the milk bottle. He looked at the bottle and made the sign again. I am so surprised that he could sign so soon, since I only showed him that sign a few days ago and only three times in total.
I remember signing to Marcus when he was about 10 months old and he picked up many signs within days. So was going to wait till Nicholas is older to sign to him. Now with this progress, it is a good motivation for me to sign properly with Nicholas.