Awkward pause before saying hello?

So this might sound weird but, there's this one guy I know who will always kind of pause and make eye contact for a second or two with me when he sees me before actually saying hi. For some reason, the hi or hello comes never immediately or naturally like it does with other people. We always seem to have that awkward pause or awkward silence before saying hi to each other. Any idea why that is?
Awkward pause before saying hello?
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