I am very sorry to hear about your pup's refusal to eat, lip licking, shivering, and eating grass.
Dogs with nausea or gastroesophageal acid reflux often lick their lips, refuse to eat their food, and may eat grass or foreign material to make themselves vomit. They will often swallow repeatedly and lick things trying to soothe their nausea and acid burn. If they can rid themselves of whatever is irritating their stomach that way then all is good.
But because he is continuing to be uncomfortable we need to stop him from eating any more grass. It becomes a vicious cycle where the more grass he eats the more his stomach is irritated and the worse he feels.
Possible causes of nausea causing grass eating include a change in diet, dietary sensitivities or allergies, or eating things that they should not like too many fatty table scraps or garbage, bones etc., a viral or bacterial infection, or a gastrointestinal blockage from eating indigestible things (toys, wood, stones), Addison's which is a poorly functioning adrenal gland is another possibility for waxing and waning vomiting and/or nausea. Since he's a younger pup metabolic organ failures (kidney or liver disease), pancreatitis, inflammatory bowel disease or even infiltrative cancers are possible causes but much less likely.
Has he eaten anything he should not have recently (toy pieces, bones, garbage)?
Any changes in food or treats?
Is he current on his vaccines?
You can give him an acid reducer to try and settle his stomach. Either:
1) Pepcid-ac (famotidine) at a dose of one half of a 10mg tablet per 10 to 20 pounds of body weight every 12 hours.
2) Prilosec (omeprazole) at a dose of one half of a 20mg tablet per 20 to 40 pounds of body weight every 24 hours.
These will reduce stomach acid and could help settle his stomach. These can be used for several days if necessary as they are very safe.
I'd also pick up his food and water for now. A couple hours after the giving one of the acid reducers you can offer small amounts of water or ice cubes to lick.
No food for 12-24 hours. Small amounts of water only.
After his food fast then start a bland diet of 1/3 boiled, lean hamburger (or boiled, white, skinless chicken) and 2/3 boiled white rice. Give small meals several times a day. Feed the bland diet for several days, then start mixing in his regular diet and slowly convert him back.
If his nausea continues then he may need injectable medication from a veterinarian to get his stomach upset under control.
So watch him for continued lethargy and vomiting even with the acid reducers, blood in his stool or vomit or a fever (more than 103.5F rectally), a tense painful belly or lack of appetite after his food fast. If any of those occur it is time to seek hands on veterinary care.
It would also be a good idea to have blood tests done as well to make sure there isn't an underlying metabolic problem like Addison's disease present.
Please let me know if you have any further questions.