We should start with the rule regarding presentation of search warrants. The US Court search and seizure warrant form explicitly says
Unless delayed notice is authorized below, you must give a copy of the
warrant and a receipt for the property taken to the person from whom,
or from whose premises, the property was taken, or leave the copy and
receipt at the place where the property was taken.
State will have similar rules, e.g. Washington's CrRLJ 2.3.
(d) Execution and Return with Inventory. The peace officer taking
property under the warrant shall give to the person from whom or from
whose premises the property is taken a copy of the warrant and a
receipt for the property taken.
This does not explicitly say "before starting the search," and the wording "shall give ... a copy of the warrant and a
receipt for the property taken" implies that the two documentary items can be presented at the same time (therefore after the search). Arkansas's rule Ark. R. Crim. P. 13.3 is slightly different
(b) Prior to entering a dwelling to execute a search warrant, the
executing officer shall make known the officer's presence and
authority for entering the dwelling
which is not a requirement to present the warrant itself, and then
(c) In the course of any search or seizure pursuant to the warrant,
the executing officer shall give a copy of the warrant to the person
to be searched or the person in apparent control of the premises to be
searched. The copy shall be furnished before undertaking the search or
seizure unless the officer has reasonable cause to believe that such
action would endanger the successful execution of the warrant with all
practicable safety, in which case he shall, as soon as is practicable,
state his authority and purpose and furnish a copy of the warrant.
So there is some variation in the requirement for handing over a copy of the warrant.
Body searches might be subject to different standards per jurisdiction. Washington search law has extensive limits on strip and body cavity searches, whereas searching pockets is like searching a premise (a copy of the warrant must be eventually presented, along with an inventory of items seized).
It is typically stated that ideally, police will show a copy of the warrant to the person being searched or whose premise is being searched, but ideally does not mean "must always". I have not found any case where an officer reasonably could have shown the warrant prior to conducting a search (when so requested by the searchee) but unreasonably refused.