I don’t know whether due to my disability, my health conditions or my medications, but for a few years now I have not experienced ‘morning-glory’; until, that is, this past couple of weeks on an almost daily basis.
Nocturnal penile tumescence (NPT) is experienced by most men, although as the phenomenon can occur at any time, not simply during the night, the official name is a bit of a misnomer. I prefer the less common term ‘tonic erection’ (tonic in this sense relates to physiological muscular contraction). Such erections usually occur during sleep, particularly the REM phase. Typically a man will experience five such occurrences during his slumber. They are not thought to be essentially about sexual arousal. Indeed, any man who has awoken with his ‘morning-wood’ will know that it is frequently ‘piss-hard’, that is erect until he has urinated. Micturition allows the muscles around the penis to relax. It is believed this is one of the reasons tonic erections occur: to prevent enuresis or bed-wetting. So those partners complaining of being poked in the lower back first thing of a morning, may have to be a tad more understanding!
Non-sexual erections can occur in other situations too. For example, I recall my sex-education teacher explaining, with a bright red face, that he himself used to get erections whenever he travelled on a ‘bus, because of the vibrations coming up through the seats. Been there myself and found avoiding sitting near the wheels helped. Until my teacher explained, I thought I was some kind of weird pervert!
Electro-stimulus can also induce an erection. Whilst this is not necessarily sexual, some men use such processes to get their kicks. So if one should come across some unusual equipment in the back of a drawer, or wherever, this may be what it is used for!
One further issue relating to non-sexual male physical arousal is priapism. This is where a man remains tumescent for a minimum of four hours without intending to do so (so we are not talking tantric sex here). Being priapic is painful and is not concupiscent. One should seek medical assistance where the condition persists.
Erections are on the whole perfectly natural. Just accept them and don’t worry!