Actors always say they can't wait to do theatre, rather than television.
But that's often because television has become a recalcitrant lover who doesn't write or phone any more.
In Sharon's case however, TV continues to adore her, as evidenced by work in dramas such as New Tricks, Mistresses and The Inspector Lynley Mysteries.
So when the Glasgow-born actress does appear on the stage – from today she's starring in Oran Mor's lunchtime theatre show Astonishing Archie – you know it's not because her options are limited.
"I love theatre," she says, the enthusiasm in her voice audible.
"In television, you don't really get cast too far from where you are in real life.
"Scenes aren't shot in sequence, and the acting is all done in short bursts.
"But theatre takes chances with casting. And because it's so much more verbal, it offers the chance to express so much more.
"What I love about theatre is the chance to play out a story, get into a character.
"And once the play is completely inside me, and I feel I've got the measure of the audience, the theatre feels like a playground."
Sharon's playground this week is Astonishing Archie, written by and starring Bill Paterson.
The play tells of the great musical divide of the 50s – Sinatra or Elvis.
Those whose formative music years were the late 1940s simply loved the crooners, but the youngsters who grew up in the 50s followed a new star.
Set this conflict in Glasgow, where two brothers born 10 years apart argue about the choice of funeral music, and you have the dramatic narrative for a clever play.
"My role is to be the calm voice," says Sharon, smiling.
"I'm the minister, the mediator between the warring brothers so I don't really show a great range in this performance.
"But it's a real challenge and I get to appear alongside Bill Paterson and Kenny Ireland."
It's obvious Sharon is an actress who can inhabit characters. But she smiles as she admits sometimes the stage characters can impact upon her own personality.
"It can happen," says the mum of two young boys.
"When I appeared in Men Should Weep (at the National, 2010) although life was miserable for my character what I did take from her was that she was a bit more loving than me."
She adds, grinning: "I think during that run I became a bit more loving than normal."
Sharon was born in Glasgow but the family moved to Fife.
"I wasn't one of those (sings) 'To-morrow! To-morrow...' stage school kids, although I would show off about the house.
"Later, when I went to see my career adviser she asked me what I wanted to do and I said (sad, appealing, apologetic 15-year-old voice 'An . . actress?'
"She replied 'So why are you studying Physics?' But at the time – she's 45 – there was no drama at school and the arts wasn't encouraged."
However, when Sharon went along to see the Wildcat Theatre's production of the Beggar's Opera at the Lyceum in Edinburgh she had her epiphany.
This was the world she wanted to be part of.
She said: "I saw people dance, pick up a saxophone, act. I thought 'I need to do this.' I didn't know if I could do it but I was desperate to find out."
Sharon completed a drama course in Fife and moved to London to study at the Mountview Academy of Theatre Arts.
She graduated in 1989 and has been lauded by theatre critics since, while playing the Donmar or the National.
ON TV, if Sarah Parish or Sarah Lancashire isn't cast in the 30s/40s weighty female role, you can be sure it's Sharon.
And she's equally excited and trepidatious about appearing at Oran Mor for the first time.
"I've no idea what it will be like to step on that stage," she admits.
"For years I've wondered why I've never appeared in the Play, Pie and a Pint series and now I'm about to find out."
She adds, laughing: "If you see me at the bar and I seem very calm, it means the minister has affected me."
n Astonishing Archie, Oran Mor, until Saturday.