"think of a time" is correct and usable in written English.
You can use it when you want to prompt someone to recall a past experience. For example, "Think of a time when you felt truly happy and free."
Can anybody think of a time when they have done that?
Ed and Eva Donohue can't think of a time when their daughter wasn't running.
TS Eliot wrote, "We cannot think of a time that is oceanless".
Can you think of a time when you have adapted to a new situation?
— but I can't think of a time when a party's economic doctrine has been so completely divorced from reality.
Try to think of a time when food, or a particular meal, has been important to you.
I can't think of a time I felt worse for my brother photojournalist than covering the John Edwards trial.
Can you think of a time when a famous artist or performer stood up for something and created positive change?
The couple couldn't think of a time they had visited a place or eaten anywhere outside the casinos.
It is quaint to think of a time stores did not open and liquor was not sold on the Sabbath.
"I can't think of a time when there's been greater pressure to deliver evidence to order," he said.
