If the nest promises to be more empty than usual this holiday time, or if you simply feel like chucking all the obligations of the season, your Christmas can still be merry. A whole array of nearby country inns with a warm personal atmosphere are waiting to make you welcome, a guest with nothing to do but enjoy Christmas. And if you prefer the big resorts, they're all decking the halls and shining the wassail bowl in hopes of entertaining you.

The bad news in all this cheery preparation is that many -- though not all -- are already fully booked. But believe it or not, it's not too early to be thinking about accommodations for the 1981 Yuletide season. Many holiday guests are repeaters and space gets very tight.

Colonial Williamsburg, Va., is naturally gearing up for its usual 18th-century festivity replete with Yuletide customs that have come down to us from England. Williamsburg serves up a traditional Christmas of the finest variety, complete with boar's head, costumed carolers and Della Robbia wreathes. And at this writing there is even room at the inn.

A cannon will signal the official opening of the two-week celebration beginning Dec. 14, and the show will be splendid. Duke of Gloucester Street will be bedecked for the holiday with candles glowing from every window in the historic area and bonfires lending their light to dancers and balladeers, musicians and carolers. The Capitol will host two concerts that evening and the Lodge Auditorium will feature an 18th-century play.

Music will be in the air every day from then on, with fire and drum, concert and street caroling. For children there will be pie-eating contests, racing and the challenge of a greased pole with a prize at the top. All seven of Colonial Williamsburg's restaurants will be spreading a groaning board and the Lodge is planning a Baron's Feast, a tradition handed down from the English nobility who used to entertain those who worked their lands at Christmas. The Williamsburg version is complete with a baron to head the cast.

The Boar's Head Inn, in Charlottesville, Va., also puts on a show at Christmas that would please even Mr. Pickwick, but reservations are so tight that it may be you'll have to wait until next year. Here in Jefferson's county they take price in bringing a bit of Merrie Olde England to Virginia, with ministerls, madrigals, mummers and Morris dancers, enough to make you lose track of which century you are in.

The Lord of Misrule is in charge and he encourages guests to help him search for a Yule Log. The mummers will be presenting a medieval mystery play and the Morris dancers will perform ancient figures associated with the winter sostice. As part of the inn's annual tradition, the large colony of waterfowl will get a Christmas handout of corn, and afterwards guests can get a look at the surrounding countryside by stage coach.

The inn's Feast Before Forks may well prove a challenge, since among the courses offered for consumption without forks are rybbys of beef, gret Mete pyes, Cornish byrdys and pudding of Plumme. And before you go home, the Boar's Head will see that you eat a cumin seed roll in the shape of a horseshoe to honor the patron saint of horses and ensure a safe trip and speedy return.

The Homestead, in Hot Springs, Va., always does Christmas up right, of course, and provides an old-fashioned holiday with show and mistletoe and the biggest Christmas tree south of the Ellipse. There'll be sleighs to snuggle in under blankets, a ski competition to watch, carol singing and a reception for all guests on the evening of the 23rd. Children and teen-agers will have their own events and it all winds up with a New Year's Eve black-tie gala. Rooms were still available two weeks ago.

The Greenbrier, in White Sulphur Springs, W. Va., doesn't want anybody to feel lonely at the holidays and has arranged for guests who'd like to meet new acquaintances to sit at the Holly tables in the dining room where between 10 and 14 people will be seated. New friends made here will help you enjoy the musical programs, dancing exhibitations, wine-tasting and the rest. Santa Claus is scheduled to arrive either by sleigh or carriage on Christmas Eve at the hotel's front door.

On a smaller scale, the Country Inn in Berkeley Springs, W. Va., is waiting to give you a truly old-fashioned welcome at Christmas. This is a warm and cozy inn at any time of the year, but during holidays the management outdoes itself. There's something about sitting around a woodburning stove, toasting your toes amid the sweet scent of hemlock that seems especially right at the holidays. House guests will be getting together to drink eggnog and eat homemade cookies while Christmas carolers sing the old songs to an organ accompaniment. The nice thing about all this is that, at this writing, there were still a few reservations available.

In planning your holidays don't overlook the Inn at Phillips Mill in New Hope, Pa. It's booked solid for this year, but you can make reservations for next year. This is the place to snuggle up to an open fireplace and enjoy the smells and sights of Christmas. If you were there this year, what you'd sniff would be roast goose with chestnut dressing and what you'd see would be a Christmas tree in each room downstairs, one trimmed with calico pigs (the sign of the inn) and one decked exclusively in cookie cutters. cLucky guests will be toasting each other with hot grog.

Closer to home, the Wayside Inn in Middletown, Va., is another inn which takes Christmas seriously.

"There's something about a country inn that makes a real, warm, happy time at Christmas," says Marjorie Alcarese, innkeeper of the wayside, and she has seen to it that her guests will lack for nothing. Elizabeth Taylor Warner is among the judges invited to pick the best handmade Christmas ornament in the annual competition in which guests and townspeople alike compete. The inn will be decorated with the entries and everybody can pick his favorite before the $50 prize is awarded. Losers can save their disappointment with the ambrosia pie for which the inn is famous.

The Hotel Strasburg, in Strasburg, Va., calls itself a hotel but it is as much an inn as any with its charming Victorian decor and its pleasant, old-fashioned ways. It has stood at the corner of Queens and Holliday Streets for nearly a century and is planning a Christmas to suit. Guests will make each other's acquaintance over punch and cookies, and the pine-paneled Depot Lounge, with its stained-glass windows and huge bar, will be echoing the sound of holiday music played on the old upright piano. There'll be plum pudding and something special on each of the 12 days of Christmas, and carolers will be dropping in often. The good news here is that a few of the rooms, with their old brass and iron beds and 19th-century antiques, were still unspoken for.

The Fairfield Inn in Gettysburg, Pa., is moving Christmas festivities up to the first Sunday in December, when it is holding its Feast of Christmas. The Yule Log will be rolled out and the boar's head brought in at an annual celebration which has become a tradition. Every year guests return and the feast is sold out for this year. For Yuletide 1981, the books are wide open. If you're quick enough, you might even get one of the six rooms the inn offers.

"Christmas?" said Harry Nessler, innkeeper at the famous 1740 House in Luberville, Pa. "What I give 'em is peace and quiet. They can sit in front of a roaring fire, look out at the river and get away from all that tinsel."

If that sounds like Scrooge, it doesn't much matter. What the 1740 offers is a retreat from the holiday madness, and there couldn't be a better place to get away from office and parties and canned Christmas carols on loudspeakers. You won't even be bothered by Yuletide TV programs because there aren't any televisions at the 1740. Nessler said he still had a few rooms left for the very special guest who wants to escape from it all.

The Tidewater Inn in bucolic Irvington, Va., will, on the other hand, be putting on quite a show. This waterside inn would like to bring a feeling of family warmth to people who will not be hanging stockings at their own or relatives' chimneys, so it's scheduling a party every day to keep things merry. rThe inn will be hosting a Christmas harp concert, a glorified tea, an eggnog party, and on Christmas Eve, the wassail bowl and Yule Log ceremony at which each guest is invited to throw a sprig of green on the blaze for good luck and fellowship.

Santa Claus, elsewhere often the exclusive property of children, will be handing out a present for each guest. Besides all this there'll be lunches as usual on the Miss Ann, the 127-foot cruiser berthed at the inn's dock. Well, no, there's no room at the inn this year, but think 1981.