The 34-year-old, who came third in Athens in 2004, has concentrated on the 400m hurdles since November 2010.
She failed to qualify for the World Championships and has since lost her lottery funding, but began training for multi-eventing again four weeks ago.
"I am motivated more and I'm enjoying the fact I could be at the Olympics in the heptathlon," she told Sky Sports.
"It has rejuvenated my feelings for the sport."
Sotherton later said on her Twitter account: "I've had to keep my gob shut for over 2 months about this! So it's a relief it's out! #heptathlon"
Since ending her hepathlon career, Sotherton has been supplanted as British number one by Jessica Ennis and she has previously said that, at her best, she could have run the 2009 world champion from Sheffield close.
Sotherton admits that she does not expect to challenge Ennis on her comeback.
"I don't think I'm going to be rivalling her as I possibly could have been a few years ago. I know where my limits lie, I'm not striving for a gold medal," she added.
The Olympic 'A' qualifying standard is 6,150 points, comfortably below Sotherton's 2005 personal best of 6,547.
She scored 6,517 in her last heptathlon in 2008 before heel and back injuries forced her  withdrawal from the multi-discipline event.

Abbie Bloodworth, 19, died after a blaze broke out at a house in Cwmparc, Treorchy, just before 12:00 BST on 19 August.
In a family tribute, her mother, Samantha Dorricott said: "Abbie was my rock, my world and I miss her deeply."
The cause of the fire is being investigated by the fire service and South Wales Police.
"She was a fabulous and loving mother to her three-year-old daughter Chantelle," added Ms Dorricott.
"She was kind, funny and had a heart-of-gold."

Earlier this month, Songbird, which owns 69% of Canary Wharf Group, advised its investors to reject the offer.
On Wednesday, it said it still believed the 350p per share offer was too low.
"The offer does not reflect the full value of the business, its unique operating platform and its prospects," it said.
Qatar Investment Authority (QIA) and US investor Brookfield Property Partners made the offer.
QIA already owns 29% of Songbird, but had to persuade the next three biggest shareholders, New York-based Simon Glick, sovereign wealth fund China Investment Corp and Morgan Stanley, who own more than 50% between them to accept the offer.
Songbird said it was now its understanding that "each of the major shareholders intends to accept the offer".
It also said the board had been in discussions with a number of parties "with a view to achieving a higher offer", but said it now believed none would be forthcoming before the 29 January offer acceptance deadline.
Canary Wharf was established 25 years ago as the new financial district in London, and is home to some of the world's biggest banks including HSBC and Barclays.
In the UK, Qatar owns Harrods, Chelsea Barracks and the Shard, Europe's tallest skyscraper.
QIA was founded in 2005 by the state of Qatar to help its economy by investing in a diverse array of businesses, outside of the country's huge oil and gas resources.
Former Olympic bronze medallist Kelly Sotherton is to return to heptathlon and hopes to compete at London 2012.
[NEXT_CONCEPT]
A young mother who died in a house fire in Rhondda had "a heart of gold".
[NEXT_CONCEPT]
A Qatari-led bid has won the battle to take over London's Canary Wharf complex after three of its major shareholders agreed to accept the Â£2.6bn offer.