Usually I just show up and check in. If the hotel has been busy rooms will not be ready otherwise they will check me in right away.
Its 3pm. But they can do early check-in if they have availabilities. You if have the Marriott app you can request early check-in as well. They will be more willing to make you a priority with a Marriott Rewards membership
I was able to check in at 1pm
3pm
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