Yes, there is a timer option when assigning a worksheet as a task to your students.
When assigning a task you have the Dates and duration tab where you can assign:
start date: to make the task only available on a specific date
end date: task will be available only until this specific date
duration: once a student access the task link a timer with the specified minutes will start counting down. Students must send their answers before running out of time
You can see all those parameters in the screenshot below.
Any of those parameters will help controlling the time a task can be done.