Bask in place
The only critical task you've highlighted (one that can't go unattended or robot-operated for four hours) is piloting/navigation. Those are stationary activities.
Naturally, the cockpit/control deck/wherever the aliens do their piloting and navigation from have infrared lamps installed over each of the critical positions. When the shift changes, the incoming crew member smacks the "basking" button, the infrared comes on and warms them up as they begin their shift and do their duties. After a four hour timer, the lamps shut off, until of course the first crew comes back on the next day and smacks the button for their basking-at-work session.
If modesty is an issue, and the aliens need full-body basking (i.e. no clothes), there are two options:
The aliens have developed an infrared-transparent fabric. It may not be the most comfortable, but for these crew duties, it allows for appropriate modesty while basking at their station.
The cockpit or control deck is isolated from the rest of the ship, at least visually. When the critical crew comes in for their shift, they strip down so they can bask while working. The furniture will be made of materials that are more comfortable against bare skin/scales and easier to sanitize, and the crew will each understand that their work situation requires them to be naked on the control deck and will thus forego normal societal modesty while working.