You cannot simply walk into a sheriff auction and raise your hand. Registration comes first, and it has teeth.
Expect to produce FICA documents, which in practice means identification and proof of your residential address, and to pay a registration fee. The fee is refundable if you do not buy. There is a registration form to complete before bidding opens, and the rules of auction are available for inspection beforehand.
Some sheriffs require the registration fee by EFT in advance rather than in cash on the morning. That is the requirement most likely to catch you out, because the deadline then falls days before the auction rather than on the morning of it, and there is no counter you can pay at once bidding has started.
None of this is unusual and none of it is hostile. It exists because these auctions are regulated and the sheriff has to know who is in the room and be able to identify the person who ends up bound by a bid.
It does mean that turning up on the morning with a deposit and enthusiasm is how people end up watching a property they wanted being sold to somebody who did the paperwork on the Tuesday.
The requirements are not identical from one sheriff to the next, which is why the single most useful thing you can do is read the conditions of sale for that particular sale before the day. They state what that sheriff requires, what the deposit is, and how long you have to deliver a guarantee for the balance. They are available for inspection at the sheriff office, and the notice tells you which office that is.
The attorney acting for the creditor is the other person worth phoning. Their name, telephone number and file reference appear on the notice, and the reference is what makes the call quick rather than a search through a filing system.
Registration gets you into the room. What happens once you are in it, and what you are committing to when the hammer falls, is covered in the buyer's guide, and the money side of it works out on the bond calculator.